Sink and Dishwasher move

[Pat M]

Thank You so much for the help you have already provided from reading over the previous post. My summer project is remodeling the kitchen. The sink and dishwasher are being moved over about 8'. I am starting to plump in the sink and so far have connected the double sing to a p trap with 1 1/2 pvc. which then connects back thru the wall cavity, tee's off down to the crawl space where I connected it to 2" pvc just after the 1 1/2 90. The other tee 90's over thru the next cavity along the window and up to the attic where it will connect to the old vent. It pretty much mimmicks the current set up. I am confused about 2 things. Currently the 2" under the crawl is galvanized travels to the other side of the crawl (12') 90's another 10' and 90's down to the waste pipe. There is not a pitch to the pipe should the new one have a 1/4" pitch. If I do pitch it how would the last connection be made since it is a 90 the thread's would not line up. The second question is for the dishwasher drain should there be an "air gap". The current configuration does not have one but it does go up over the inside of the cabinet just under the countertop and connects to the wye instead of straight thru the cabinet. I hope you can make sense of my long winded question.

Thank You so much
Pat

[LazyPup]

If I am understanding your description correctly you have a drain in the wall which is dropping below the floor and connecting to an existing 2" galvanized iron pipe.

You also have a vent riser which must offset either right or left around a window before connecting to an existing vent line.

I have prepared an isometric illustration attached below-

Before we begin there are a couple points that we must discuss.

Much of the pipe used for Drain, waste & vent systems is also used for supply & distribution (pressure pipe) applications. In order to insure that we use the correct fittings they use a different method of identifying pressure and DWV fittings. Pressure fittings will have sharp right angle bends at elbows and Tees and they are identified by the angle of the change in direction expressed in Degree's. I.E. A 90 deg elbow, a 45deg elbow etc.

DWV fittings always have a slight radius curve on the bends to insure a good velocity of flow under gravity pressure. In order to insure we do not confuse DWV with Pressure fittings, DWV fittings are identified by the fraction of a circle that the change in direction makes, thus a DWV 90deg elbow would properly be called a 1/4 bend (90deg = 1/4 of a circle) and a DWV grade 45deg elbow would be called a 1/8 bend (45deg = 1/8 of a circle).

When connecting a horizontal line to a vertical line we must us a Sanitary Tee.

When connecting a vertical or horizontal line to a horizontal line we must use a Wye or Wye & 1/8bend (tee's are prohibited on horizontal lines.) The intent here is to insure the liquid will enter the horizontal line at a 45deg angle in the direction of flow so as not to reduce the velocity of flow. When we need to connect to a horizontal line at right angles we first install the required Wye, which would be at 45deg, then we install a 1/8 bend which provides an additional 45deg to get a 90 deg right angle connection. The easiest method is to use an "Street 1/8 bend". A street bend has a Hub fitting on one end and the opposite end is a raw edge the same size as the pipe so it can be inserted directly into the hub on the Wye. You will also find fittings called "Combo's". A "combo" is a fitting that combines the Wye & 1/8bend into one fitting and Combo's or Wye & 1/8 bends may be used interchangably.

All drain lines must have a cleanout on the upstream end, at each change of direction greater than 45Deg and each 100' of linear run. Begining at your sink, the P-trap is removable so may serve as the cleanout.

1-1/2" is the correct size for both the P-trap and the waste arm (Line from the P-trap to the wall)

Under the International Residential Code the vertical drop from your waste arm down through the floor may be 1-1/2". Under the Uniform Plumbing Code if you have a disposal or dishwasher connected to the sink the line in the wall must be a 2" line.

Please note in the illustration that you may not have a horizontal vent line until the vent reaches an elevation at least 6" above the flood level rim of the highest fixture served by the vent. In this case the kitchen sink is the highest fixture served and the flood level rim of a kitchen sink is flush with the counter top so the vent MAY NOT turn horizontal until it is 6" higher than the countertop. The horizontal section of the vent must be pitched 1/4" per foot with the drop in the direction of the drain line. This is to insure that any condensate liquid that might form in the vent line will flow down the drain.

NOw in regards to your galvanized 2" line.

Both the Uniform Plumbing Code & The International Residential Code list Copper (DWV grade), Copper (types K, L & M), Cast Iron-no hub, ABS sch 40, PVC sch 40 & galvanized steel as approved materials for DWV (Drain, waste & Vent) applications above grade within a structure.

Having said that, it must also be understood that with some rare exceptions due to the cost of material and labor galvanized pipe has not been installed in DWV applications since the late 1960's therefore in all likelyhood that galvanized pipe is already 45 or 50 years old. We must also consider that as the pipe ages the inner walls of galvanized pipe develope rust which then leaves a very rough surface that will catch cooking grease and solid particulates that might be suspended in the waste. This is further complicated by the fact that many galvanized DWV systems were installed with pressure fittings which have sharp bends that contribute to clogs.

The total length of that galvanized run is approximately 22' plus a half dozen fittings. In my personal opinion you could replace that entire section of pipe with PVC for less money than it would cost to rent a drain cleaning machine and clean that line one time.

[Pat M]

Thanks Lazypup right on as usual. It looks like I can confiigure everything the correct way with the exception of the vent. The window would prevent me from going up 6'' from the counter before the horizontal line. Could I use an 1/8 bend to go to the next cavity, about a 12" run, and then 1/8 bend up to the attic?
You are so right about the galvanized, the previous drain developed a rust "pimple" that leaked for a short time before my wife went in the crawl and noticed the musty smell. I replaced this at that time and will use pvc for the new one too. Regarging the pitch, from A to B would not be a problem but after B to C in your diagram how would the connection be made if it is not a 45 degree angle to match a 1/8 bend on C down to the waste? Do you have any thoughts about the dishwasher?

Thanks Again

[LazyPup]

Using the 1/8 bends will work fine.

In the Plumbing trade assuming vertical to be Zero and horizontal to be 90 degs, any line from Zero to 45 degrees is classified as a vertical line and any line from 45 degrees to 90 degrees is classified as a horizontal line.

Code requires all horizontal or commonly called "flat" vent offsets to be 6" above the flood level rim of the highest fixture served by the vent.

Below the 6" elevation you may make a vertical offset, which would be between zero and 45 degrees from vertical so you could use a pair of 1/8bends(45deg), 1/6(60deg) bends or even 1/16(22.5deg) bends to make the offset. (see attched illutration)

in regard to replacing the galvanized line. The line from point A to point B is 12 feet long and it drops 3" in the 12 foot run. From point B to point C the run is 10 feet and it drops another 2.5". The pipe itself is flexible enough to allow that pitch without causing any problem with the fittings.

At point C you will have a Wye & 1/8 bend changing the direction from horizontal to a vertical drop. Here again, you will have no problem with the fittings.

Now for the dishwasher drain line.

Under the Uniform Plumbing Code ALL dishwashers are required to have an air gap installed above the countertop. If there is a garbage disposal on the sink, the dishwasher line MUST connect to the disposal input port. A dishwasher drain line may not be connected to a drain line downstream of a disposal.

Under the International Residential Code the line from the dishwasher MUST rise as high as possible under the cabinet and be secured in place. It should then drop down to a point slightly below the point of attachment to the drain lines and rise up to the attachment. It may then be connected to a trap, trapped fixture, branch Wye tailpiece on the kitchen sink or a garbage disposal input port.

Check your local code.

[Pat M]

Thank You very much Lazy