Basement Storm Sewers

[rckowal]

Our home is in Michigan. It has 3 levels over a small basement. The basement is 8' high with about 5 ' below grade. The basement slab has two sewers - one is the sanitary; the other is a storm drain. We have a city sewer system (no septic fields).

I would like to understand the pipe layouts that are typically used in (just) the storm drain.

1. Is there a row of drain tiles (or what ever they're called) placed along the exterior side of the basement wall to catch ground water?

2. Are drain tiles used under the slab to collect ground water?

3. Do basement storm drains discharge into the house sanitary sewer on their way out to the city's sewers?

Some help here would really be appreciated.

[LazyPup]

Very good question although it is a bit difficult to give a finite answer because of all the variables involved.

Prior to World War II it was common for municipalities to discharge raw sewage into a local river, lake, bay or estuary therefore both sanitary and storm drainage was discharged into a common sewer line.

With the advent of sewage treatment plants they needed some method of determining the size of treatment facilty the city would require. Typically a family of five will produce approximately 300gal of sanitary waste in a 24hr period or 300gal/24hrs = 12.5 gal/hr. The initial treatment plant volume was then determined by multiplying 12.5ga/hr x the number of homes to be served plus a n estimate for commercial or institutional waste.

At the time no one really considered the shear volume of storm drainage. One acre of land equals 43,560sq.ft. so a 1" rainfall would produce 43,560sq.ft x 144sq.in/sq per sq.ft = 6,272,640cu.in of water. One gallon occupies 231cu.in so 1" of rainfall produces 27,154.28gal of water per acre. This means even a light 1/10" sprinkle of rain would produce 2,715.42gal of water per acre. This then meant that 1/10" of rainfall would produce as much storm runoff on an acre of street or roadway as 10 homes would produce in a 24hour period. Obviously the shear volume of storm runoff was overwhelming the treatment plants and often their holding tanks overflowed spilling raw sewage into the watershed.

While it could be argued that storm runoff does pick up some contaminants during the runoff, nonetheless, storm runoff is basically pure water and does not require treatment so the solution was to install a second set of sewer lines parallel to the first. With duel sewer lines the original lines were dedicated to sanitary waste and go to the treatment plant while the second set of lines are dedicated to storm runoff and may be discharged directly into the local water shed.

As a result, the Plumbing Codes were ammended and now they strictly prohibit discharging any sanitary waste into a storm drain or storm drainage into a sanitary sewer.

By definition a foundation footer drain, gutter & downspout drains and sump pump drains are classified as "storm drains" and may not under any circumstances be connected to the sanitary drain system.

Basement floor drains fall into a vague gray area of the codes. When practical a basement floor drain is to be connected to the sanitary drainage system however in many circumstances due to the required pitch in the house sewer line quite often a house sewer line will enter the basement at an elevation higher than the basement floor. Understanding that water will not run uphill, the codes allow an exception that under these circumstances the basement floor drains may be connected to the storm drain system and discharge into a sump crock where the water is pumped out via the sump pump.

There are a number of different methods to install a footer drain but primarily the exterior footer wall of the structure is waterproofed from finished grade down to the foundation. Typically a 4" slotted flex pipe is then laid at the bottom. The method of connecting the footer drain to the storm sewer would then be dependant upon the elevation of the footer drain in reference to the storm drain. If the elevation of the footer drain is high enough to allow the necessary pitch it may be possible to run a line directly from the footer drain to the storm drain but in most instances the footer drain is too low to achieve direct gravity flow. In that case the footer drain is then discharged into a sump crock in the basement and the water is pumped out via a sump pump.(The pump is placed in the basement to permit access for servicing and in colder climates it protects the pump from freezing.)

As a rule slotted drain pipes are not necessary under the basement floor because surface ground water only saturates the topsoil but does not significantly penetrate the subsoil and generally the foundation and basement floor slab are well below the topsoil level, however this can only be determined by the soil conditions at the actual point of construction. I have seen some soil conditions where it was actually necessary to install well points below the structure and use a well pump to extract ground water.

You may have seen a construction site where they were laying a grid of slotted drainage pipes under the basement slab and assumed that to be drainage, but that may not be the case. In recent years there has been a lot of attention given to radon and methods of controlling it. One method that seems to work very well is to install a grid of slotted pipes on the top of the subsoil under the slab. These pipes are then connected to a vertical vent pipe through the roof and in some instances they actually put a powered exhaust fan on the vent line to extract the radon gasses. The entire grid is then covered with a plastic membrane (6mil poly) to prevent any radon gasses from coming through the slab thus they are discharged through the pipe grid.

I am wondering if your question was a result of general curiosity or do you perhaps have a specific question to which we may offer some insight?

[rckowal]

Hi Lazy Pup, Wow what a reply. I am a retired Engineer so I recognize that you may be one as well. By the way, I comprehend your description & it has helped me greatly to understand the design & operation of storm sewers.

Since my initial post, I did some home work on my situation. My cities Water Department confirmed that there are seperate storm & sanitary drains in my home. I can also tell you that there is no sump pump so these are gravity flow systems. Addiitionally, the downspouts do not drain into the storm drain (just out to the soil). This house was built in 1965 so I think the drain tiles are probably crocks covered with asphalt paper, rather than the slotted ones which I believe came later.

Yes, there is a specific situation that I'm dealing with where I could use your help. I have tree roots that are some how getting into my storm drain. Three years ago, they had grown enough (plus sand had accumalated) to block the flow at the clean out trap. During a severe rain storm when a huge amount of rain fell on already saturated soil, the storm drain backed up & flooded the basement floor. Concurrently, I noticed that water was coming up through stress cracks in the slab. I had a drain cleaning tech snake the tree roots out of the storm drain trap & the water drained away in a matter of minutes.

Since then, I have been putting copper sulphate in both the storm & sanitary drains in the spring & in the fall. I also pitched the top soil around the house so surface water would drain away from the walls (it was flat or reverse pitched). This seems to have slowed down but not stopped the root infiltration.

At this point, I believe that I need to find a way to stop or severely restrict the root growth in the storm sewer system so tearing up floors, etc. can be avoided. There are two foaming root killer products available which claim to stop root growth for one year. These are Rootx & Roebics products. Their application instructions are written for use in sanitary systems (flush down the toilet, etc.) which doesn't help me much. Perhaps you have some ideas on how these products (or other measures) can be used in my situation.

As a precautionary measure, I had the drain tech here a few days ago to snake both drains again. There were some roots in the storm drain but the growth was no where near being able to block the flow as it did three years ago. This indicates that the copper sulphate has slowed down but didn't stop the root infiltration.

I look forward to your further comments & ideas. Best regards

[LazyPup]

Personally I have some very mixed emotions in regard to the foaming chemical methods of controlling the roots. You could make the argument that your lines were plugged up with roots 3 years ago and required snaking the lines but since using the chemical semi-annually there appears to be no significant buildup of roots therefore the product must be working as advertised. On the other hand, how many years had the roots built up before you had the lines snaked 3 years ago? We know the house is 41 years old but we have no historical information to indicate those lines were ever snaked before. We could then argue that it perhaps took 38 years for the roots to grow enough to be a problem, therefore the minor growth your seeing after three years is typical and the chemicals have made no difference.

My single greatest reservation against the foam products is that there is no way to determine the uniformity of the chemical dispersion. No doubt a thick foam like shaving cream would work fine at or near the point where it is initially put into the line but pipe wall friction is hundreds of times greater on a dry pipe wall than it is when the pipe wall is wetted. I forsee a situation where the foam may move a few feet into the line but the wall friction of the dry upper parts of the pipe will resist its movement and any rinse water we run into the pipe may then run under the foam and rather than actually move the foam it may be dissipating the foam from underneath and carrying the chemicals away without ever having touched the majority of the pipe walls.

Some municipalities are using a method where they run a high pressure line in the pipe with a spray nozzle on the end similar to a pressure washer spraying sideways. The chemicals are then mixed with the high pressure water and they can insure a consistant coating for the entire length of pipe being treated.

In order to fully understand the tree root problem we must consider the actual purpose of the roots themselves. The tree begins by sending out a super small filiment exploratory root often finer than a human hair. That root is searching for either water or the necessary minerals and nutrients required by the tree. As a rule roots do not effect storm sewers much because there is no water present in the pipe except during periods of rain. This fact takes me back to the original question, how many years did it take to create the problem you had 3 years ago?

Sanitary sewers are another matter altogether. Not only is there water present in a sanitary sewer line nearly constantly, the line also conveys fecal matter and organic waste. In agricultural terms fecal matter is called "Manure" and is natures way of converting organic waste into a water soluable fertilizer full of nitrogen, phosphorus and the other trace elements required by the tree so we can easily understand why the tree would concentrate root growth into a sanitary sewer line. From a trees point of veiw our sanitary sewers must appear like a goumet restaraunt or fast food joint.

I don't know the exact date when PVC pipe was first approved by the ASTM (Amercan Society for Testing & Materials) for use in sewer and DWV applications but I am guessing in the mid to late 60's, and it would have taken a bit more time to be adopted from the National Model Plumbing Codes into the local codes. PVC has the singular advantage that all joints are chemically welded by the glueing process so the fine roots cannot get into the joints.

Your house was constructed in 1965 so most likely you have Vitreous Clay Hub & Spigot pipe. Vitreosu clay pipe is an orange or reddish tile like material that has a glazed surface. The pipe was made in approximately 3' lengths with a Femal hub on one end. The opposite end was simply the raw pipe diamter called a Spigot end. The pipe is laid by starting at the discharge end where it meets the municipal sewer and working back towards the structure with the Female hub always on the upstream end toward the structure. Some local codes required the joints to be packed with oakum and in later years some of the pipe actually had a rubber collar on the inner wall of the hub to help seal the joints, prior to that much of it was just the raw pipes, one into the other leaving a minor gap between the outer wall of the pipe and inner wall of the hub. The problem with these type of joints is that it was easy for the hair fine root to get into the pipe and as the root grows it expands until it finally shatters the hub or pipe end.

Now in regards to your specific storm drain problem. We have no real documented evidence to show that the chemicals effected the growth rate, but on the other hand, the chemical does no harm either so it would be judment call whether or not to continue that. You have confirmed that the growth was minor after three years so perhaps it would be cost effective to just plan on having the lines snaked on 3 or 4 year intervals.

If you would like a permanent solution there are a couple options you may want to consider.

I would begin by having a camera run through the existing pipe to determine its present condition. If the camera reveals numerous cracks or breaks in the pipe it may be necessary to have the entire line replaced with PVC but considering that your footer drains are gravity flow and we must consider the pitch from the footer to the municipal storm sewer, the existing line must be quite deep and could be a very expensive excavation job to replace it.

An alternative method that is currently being used quite successfully by many municipalities on their sanitary sewers and storm sewers is to have the pipe re-lined. If you run a search online for sewer pipe relining you will see a number of different methods that are being used. One method which I have seen done is the Cured in Place liner. To install it they run a line inside the pipe that sprays a polymer product that coats the inner wall of the pipe and cures in place to form a solid liner.

You may want to discuss this problem with your local municipal sanitary engineer. Most cities are now saving the taxpayers untold millions of dollars by relining sewer lines rather than tear up the streets to replace them.

On a side note: I am not an engineer although I did attend college toward that end for a couple years and i would like to relate to you a humerous incident that occured while attending college.

I was sitting in the student lounge going over some notes one evening just before class when a cute young lady informed me that she was a cosmetology major and wanted to know what my major was.
I informed her that I was studying engineering and her reply was,,,,,"Who wants to work for the railroad?"

[rckowal]

Personally I have some very mixed emotions in regard to the foaming chemical methods of controlling the roots. You could make the argument that your lines were plugged up with roots 3 years ago and required snaking the lines but since using the chemical semi-annually there appears to be no significant buildup of roots therefore the product must be working as advertised. On the other hand, how many years had the roots built up before you had the lines snaked 3 years ago? We know the house is 41 years old but we have no historical information to indicate those lines were ever snaked before. We could then argue that it perhaps took 38 years for the roots to grow enough to be a problem, therefore the minor growth your seeing after three years is typical and the chemicals have made no difference.

My single greatest reservation against the foam products is that there is no way to determine the uniformity of the chemical dispersion. No doubt a thick foam like shaving cream would work fine at or near the point where it is initially put into the line but pipe wall friction is hundreds of times greater on a dry pipe wall than it is when the pipe wall is wetted. I forsee a situation where the foam may move a few feet into the line but the wall friction of the dry upper parts of the pipe will resist its movement and any rinse water we run into the pipe may then run under the foam and rather than actually move the foam it may be dissipating the foam from underneath and carrying the chemicals away without ever having touched the majority of the pipe walls.

Some municipalities are using a method where they run a high pressure line in the pipe with a spray nozzle on the end similar to a pressure washer spraying sideways. The chemicals are then mixed with the high pressure water and they can insure a consistant coating for the entire length of pipe being treated.

In order to fully understand the tree root problem we must consider the actual purpose of the roots themselves. The tree begins by sending out a super small filiment exploratory root often finer than a human hair. That root is searching for either water or the necessary minerals and nutrients required by the tree. As a rule roots do not effect storm sewers much because there is no water present in the pipe except during periods of rain. This fact takes me back to the original question, how many years did it take to create the problem you had 3 years ago?

Sanitary sewers are another matter altogether. Not only is there water present in a sanitary sewer line nearly constantly, the line also conveys fecal matter and organic waste. In agricultural terms fecal matter is called "Manure" and is natures way of converting organic waste into a water soluable fertilizer full of nitrogen, phosphorus and the other trace elements required by the tree so we can easily understand why the tree would concentrate root growth into a sanitary sewer line. From a trees point of veiw our sanitary sewers must appear like a goumet restaraunt or fast food joint.

I don't know the exact date when PVC pipe was first approved by the ASTM (Amercan Society for Testing & Materials) for use in sewer and DWV applications but I am guessing in the mid to late 60's, and it would have taken a bit more time to be adopted from the National Model Plumbing Codes into the local codes. PVC has the singular advantage that all joints are chemically welded by the glueing process so the fine roots cannot get into the joints.

Your house was constructed in 1965 so most likely you have Vitreous Clay Hub & Spigot pipe. Vitreosu clay pipe is an orange or reddish tile like material that has a glazed surface. The pipe was made in approximately 3' lengths with a Femal hub on one end. The opposite end was simply the raw pipe diamter called a Spigot end. The pipe is laid by starting at the discharge end where it meets the municipal sewer and working back towards the structure with the Female hub always on the upstream end toward the structure. Some local codes required the joints to be packed with oakum and in later years some of the pipe actually had a rubber collar on the inner wall of the hub to help seal the joints, prior to that much of it was just the raw pipes, one into the other leaving a minor gap between the outer wall of the pipe and inner wall of the hub. The problem with these type of joints is that it was easy for the hair fine root to get into the pipe and as the root grows it expands until it finally shatters the hub or pipe end.

Now in regards to your specific storm drain problem. We have no real documented evidence to show that the chemicals effected the growth rate, but on the other hand, the chemical does no harm either so it would be judment call whether or not to continue that. You have confirmed that the growth was minor after three years so perhaps it would be cost effective to just plan on having the lines snaked on 3 or 4 year intervals.

If you would like a permanent solution there are a couple options you may want to consider.

I would begin by having a camera run through the existing pipe to determine its present condition. If the camera reveals numerous cracks or breaks in the pipe it may be necessary to have the entire line replaced with PVC but considering that your footer drains are gravity flow and we must consider the pitch from the footer to the municipal storm sewer, the existing line must be quite deep and could be a very expensive excavation job to replace it.

An alternative method that is currently being used quite successfully by many municipalities on their sanitary sewers and storm sewers is to have the pipe re-lined. If you run a search online for sewer pipe relining you will see a number of different methods that are being used. One method which I have seen done is the Cured in Place liner. To install it they run a line inside the pipe that sprays a polymer product that coats the inner wall of the pipe and cures in place to form a solid liner.

You may want to discuss this problem with your local municipal sanitary engineer. Most cities are now saving the taxpayers untold millions of dollars by relining sewer lines rather than tear up the streets to replace them.

On a side note: I am not an engineer although I did attend college toward that end for a couple years and i would like to relate to you a humerous incident that occured while attending college.

I was sitting in the student lounge going over some notes one evening just before class when a cute young lady informed me that she was a cosmetology major and wanted to know what my major was.
I informed her that I was studying engineering and her reply was,,,,,"Who wants to work for the railroad?"

I've lived in this house for 37 of the 41 years since it was built. I can tell you with certainty that neither the storm or sanitary sewers were ever snaked out before 3 years ago. And that was in the wake of an extreme rain storm which caused the backup into the basement.

I've called the Engineering Department in my city and got no where. In fact, they don't usually return phone calls. I get the idea that they feel their job is code compliance rather than home owner assistance.

The idea of the camera to probe the condition of the pipes occured to me as well. There is still the problem of not being able to negotiate any thing upstream towards the source (roots in footer drain tiles). That's only going to show about 15 feet of storm sewer pipe between a floor drain & the clean out. Sounds like "I'm stuck between a rock & hard place".

I like your story about the cute young lady who couldn't understand why anyone would want to work for a railroad. My wife always says that she likes being mariied to an Engineer because they can be so handy around the house. However, she also quick to point out her pet peeve about them which is "Ask an Engineer what time it is & he'll tell you how to build a watch".

Thanks for the help, it's appreciated.

[LazyPup]

You don't mean to say that there are people out there who don't know how to make a watch?..LOL.

Based upon the evidence you have given I think you are worrying about the footer drain unnecessarily. (I have prepared and attached an illustration that may you provide you some insight to your situation.) As you can see from the illustration, any water that enters the footer drain would go directly to the house "Storm Sewer" where it would then follow the path of least resistance and flow down the house storm sewer to the municipal storm sewer. In order for water to backup into the basement one of two conditions would have to occur.
1. The house "Storm Sewer" become obstructed
or.
2. The Municipal storm sewer becomes overwhelmed and water is backflowing up from the municipal storm sewer.

As you can see from the illustration, your cleanout is positioned so you can snake the house storm sewer line from the house to the municipal storm sewer.

Now let us review the evidence.

1. You have lived in this house for 37 years and with the singular exception of 3 years ago you have never had a problem with the storm sewer or sanitary sewer lines.

2. Both the storm sewer and sanitary sewer lines were initially laid at the same time and most likely using the same material located in very close proximity to each other.

3. Under normal circumstances the storm sewer line would remain dry except during periods of rain whereas the sanitary sewer is constanty conveying water therefore if the problem is associated with tree roots it should be much more pronounced in the sanitary sewer line, and such is not the case here.

4. You stated that your problem 3 years ago was after an exceptionally heavy period of rain.

Based upon these facts I would be more inclined to think the real problem was backflow from an overwhelmed municipal storm sewer. If this was a repetitive problem I would consider installing a backflow preventer on the storm sewer line, but personally I don't think one incidence in 37 years would justify the expense.

Now let us consider some additional facts about the perimiter footer drain.

Initially a footer drain is required because all the soil near the foundation was excavated to build the footer and footer wall. This means that initially the soil in that area is backfill, which is very porous so any ground water falling in that region would quickly soak to the base of the wall. After 40+ years of settling and compaction we can now assume that the soil in the close proximity of your foundation has by now resorted back to the condition of Undisturbed soil thus water penetration should be minimal. In fact, digging the soil out to replace the footer drain could introduce more problems.

The first precautionary steps you might consider is to add topsoil fill near the foundation wall so that the elevation is about 4" to 6" higher at the wall and pitching out about 4' to 10' away from the foundation.

If you determine that you do need to replace the footer drain, rather than dig all the way down to the footer you could dig parallel to the foundation to a point slightly below your average frost depth then install a waterproof membrane attached to the footer wall and extending outward in your trench. You would then lay a 4" perf line and connect it to the house storm sewer line. You would then backfill over the pipe with 12" to 18" of pea gravel covered with a permeable membrane and backfill, then topped with topsoil.

[rckowal]

You don't mean to say that there are people out there who don't know how to make a watch?..LOL.

Based upon the evidence you have given I think you are worrying about the footer drain unnecessarily. (I have prepared and attached an illustration that may you provide you some insight to your situation.) As you can see from the illustration, any water that enters the footer drain would go directly to the house "Storm Sewer" where it would then follow the path of least resistance and flow down the house storm sewer to the municipal storm sewer. In order for water to backup into the basement one of two conditions would have to occur.
1. The house "Storm Sewer" become obstructed
or.
2. The Municipal storm sewer becomes overwhelmed and water is backflowing up from the municipal storm sewer.

As you can see from the illustration, your cleanout is positioned so you can snake the house storm sewer line from the house to the municipal storm sewer.

Now let us review the evidence.

1. You have lived in this house for 37 years and with the singular exception of 3 years ago you have never had a problem with the storm sewer or sanitary sewer lines.

2. Both the storm sewer and sanitary sewer lines were initially laid at the same time and most likely using the same material located in very close proximity to each other.

3. Under normal circumstances the storm sewer line would remain dry except during periods of rain whereas the sanitary sewer is constanty conveying water therefore if the problem is associated with tree roots it should be much more pronounced in the sanitary sewer line, and such is not the case here.

4. You stated that your problem 3 years ago was after an exceptionally heavy period of rain.

Based upon these facts I would be more inclined to think the real problem was backflow from an overwhelmed municipal storm sewer. If this was a repetitive problem I would consider installing a backflow preventer on the storm sewer line, but personally I don't think one incidence in 37 years would justify the expense.

Now let us consider some additional facts about the perimiter footer drain.

Initially a footer drain is required because all the soil near the foundation was excavated to build the footer and footer wall. This means that initially the soil in that area is backfill, which is very porous so any ground water falling in that region would quickly soak to the base of the wall. After 40+ years of settling and compaction we can now assume that the soil in the close proximity of your foundation has by now resorted back to the condition of Undisturbed soil thus water penetration should be minimal. In fact, digging the soil out to replace the footer drain could introduce more problems.

The first precautionary steps you might consider is to add topsoil fill near the foundation wall so that the elevation is about 4" to 6" higher at the wall and pitching out about 4' to 10' away from the foundation.

If you determine that you do need to replace the footer drain, rather than dig all the way down to the footer you could dig parallel to the foundation to a point slightly below your average frost depth then install a waterproof membrane attached to the footer wall and extending outward in your trench. You would then lay a 4" perf line and connect it to the house storm sewer line. You would then backfill over the pipe with 12" to 18" of pea gravel covered with a permeable membrane and backfill, then topped with topsoil.

Thanks again Lazy Pup, I'm really learning a great deal from your comments.

Your illustration of a footer drain & house storm drain is a lot like what I believe we have here (for the basement by itself, not the entire house). Although I don't know for sure that the field tile layout is like your drawing, the cleanout & floor drain locations are the same.

Using it as a reference, I can say with absolute certainty that the backup from the storm drain three years ago was caused by tree roots blocking the storm drain at the house cleanout. Water was backing up out of the floor drain. When a ball of fine tree roots, mixed with sand, was removed from the cleanout, all of the backed up water drained right out to the municipal storm sewer. The line between the cleanout & municipal storm sewer was then tested with water from a garden hose at both the floor drain as well as the cleanout. In both cases the water drained freely with no backup what so ever.

There is no question that very fine tree roots and sand deposits are forming in the cleanout. From what I can see, the roots are coming from the direction of the field tiles, or the floor drain - not the municipal storm sewer. About a week ago, as a preventative maintenace measure, a wad of roots & sand measuring about 3"x6"x2" thick was removed from the cleanout. This is what apparently formed in the three years since the last cleaning.

An additional preventative step I have taken already, was as you suggested. After the backup flood three years ago; I added top soil so there is a downward pitch away from the walls of about 3 - 4" in 1 - 2 feet.

I don't know that it would have any bearing on your visualization of the storm drains here, but I don't think there are footer drains at all four walls of the basement. Due to the design of this quad level home, the wall at the right of your illustration is adjacent to a family room, about 5 steps up from the basement. The top side side is adjacent to an attached garage at ground level. The only tree here is located about 15 - 20 feet (to left) from the wall at the lower left edge.

Because it appears that the tree roots are originating in the field tiles & growing towards the cleanout, I am concerned that; in time, those roots might completely obstruct the field tiles. What do you think?

Best regards

[rckowal]

Hi LazyPup,

Taking your lead, I've attached two photos of the root wad that was removed at the storm drain cleanout. It was protruding from what appeared to be an opening on the side where the the floor drain discharges into the cleanout.

One is a view of it laying on its side. The other shows an edge after it was cut to expose the center. The sand & hair roots are readily visible.

I've also included a diagram of the basement area showing how I believe the storm drain pipes are probably arranged.