house traps.

[Rewired]

This is a question directed to Lazypup...
I read your posting on how house traps are bigtime illegal because they can not allow the proper venting of methane gas from the municipal sewer system. Makes sense to me. But what I am wondering is in the city I live in now, they USED to have all house drains, roof and eavestrough drains,weeping tiles and street storm drains go into a "combined" sewer... All houses had house traps back then too.
Since the late 50'or early 60's they have went to a system where there is a "storm" and a "sanitary" main under the street, "sanitary" being for all fixtures and drains within the house, and the "storm" serving all the street storm drains as well as roof drains, eavestroughs and weeping tiles of a house or building..
In my house and several others I have seen, the "sanitary" sewer no trap in it, but the "storm" sewer connection DOES!
My question is why would there be a need for a trap in a storm sewer main? Any reason you can think of? I am just curious..
Also I just wanted to make a note, I have never seen a "house trap" with the two cleanout plugs and made of cast iron used up here in Canada, well not in this city anyway, all the ones I have seen are a fitting I think is called a "running trap" and are made of clay. There is just one plug for that sewer line sticking out of the floor and if you have a clog down the line you have to snake through the trap itself to get to it!

[LazyPup]

Municiapal storm sewers are typically run parallel to the street or roadway and almost directly under the curbing. At some predetermined interval, usually at or near a street corner or about every 400 linear feet they install a concrete vault with a storm grate opening on the curb to allow the water on the street to enter the storm drains. Those curb grate inlets and the holes in the manhole covers serve as the vents for the storm drainage system. The entire storm drainage system is pitched in such a manner as to insure that there should be no appreciable amount of water standing in the lines except during actual storm runoff, therefore the inside of the storm drains remain fairly dry.

Methane gas is formed as a result of bacterial action as bio-degradable wastes break down in a composting manner. Since their is no appreciable amount of biodegradable waste or water present in storm drains the formation of Methane gas is minimal, and what little is present would quickly dissipate through the storm grates.

Due to the high concentrations of Methane gas in a septic sanitary sewer line, the code requires that the house sewer and main drain must be provided a minimum of one main vent that runs undiminished in size up and out through the roof. In turn, every fixture attached to the drain system must have a trap. The reasoning is that the fixture trap will keep any sewer gasses confined in the sewer, house drain or main vent until they can be properly vented to atmosphere through the main vent. There can be no trap or device connected to the house sewer, house drain or main vent that would restrict the free movement of air both in and out of the vents and drain lines.

Storm sump pits, weep drains, storm floor drains and gutter and downspout drains are all required to be open to atmospheric air at their point of origin and they are required to be pitched in such a manner as to insure there can be no standing water in those drains. Basically the inside of the pipe remains dry except when actually needed to convey storm runoff. IN this manner, the liklihood of any appreciable levels of Methane in a storm drainage system remains almost nil, however, Methane gas is a heavier than air gas. In some rare circumstances there is a bit of water standing in the storm drains, along with bits of biodegradable materials such as leaves or grass that can break down and form a minor amount of methane. In some instances such as in hilly communities some of that minute amount of methane can settle to lower parts of the storm drainage system and could ultimately get into a house storm drain line if that house were at a low point in the system. For that reason, some communities require a main trap on the house storm drain to insure no gasses from the storm drain could get back to the house, since the house storm drain has no main vent.

Another concern is that in some older communities many of the old houses still have the combined storm and sanitary waste lines which could also result in methane getting into the storm drainage systems.

In my area the county is now undertaking a major project to install colored die tablets in house gutter systems. They are then monitoring the sanitary sewers to detect the presence of the colored die in the sanitary drains. If they determine that a house does have a combined storm and sanitary sewer line, that homeowner is being served a notice of non-compliance and they have a total of 180 days to correct the drainage system or the county is rescinding the "Certificate of Occupancy" and condemning the house prohibiting any further use as a residential structure until such time as the drains are corrected.

[Rewired]

LazyPup:
Thank you for the information!
I also found out a few things about whats under some of the streets in my city, some of which are bizarre...
In some areas that have the older "combined" sewers thay have added "storm" mains to convey runoff from the roads to a proper storm water disposal site (usually lake Ontario LOL) bit in some instances the "storm" drains will ultamately discharge into another "combined" sewer elsewhere. Also, like in the neighbourhood I live in, there are separate storm and sanitary lines, but eventually they are tied intogether and run into a "combined" system.. (bizarre I'd say).
This city has also spent big dollars on preventing combined sewers from overloading the treatment plant by building MASSIVE tanks underground to contain combined sewage during a storm and feed it into the treatment plant after the storm is over.
Also there was a concern a few years back where there were a lot of "cross connected" storm and sanitary connections in a few neighbourhoods, the cross connections actually being at individual residences!.. The City used of all things a smoke bomb and a blower arrangement that would sit on top of a manhole and force smoke into the sewers.. They could easily see what houses had been cross connected... Just hope no one had any dry traps at the time they were doing that[B)]