ECN Forum Forums Code Related Discussion Building Codes for Electricians American plumbing

I was chatting with Bill last night and the subject of plumbing came up.

I seem to recall reading that there are several different plumbing codes used in different regions of the U.S., and possibly a new unified code for the whole nation. \

Can anyone give a brief outline?

One point in particular which came up was the venting of drain lines. As I understand it, the U.S. plumbing codes require a vent pipe run to the main vent stack to be connected immediately at the back of every trap. Is this correct?

Paul, there are different "standard" plumbing codes in the USA and like with the NEC, different states/counties/cities can have amendments to the different "standard" codes.

Venting varies with the different codes. The UPC(Uniform Plumbing Code) requires every fixture to have a vent. The vent can tie back into a main vent stack, run independently or connect with another vent, to run up past the roof.

Some codes allow "wet venting", using a drain pipe as a vent pipe for another fixture, with little restriction, while the UPC allows wet venting on vertical pipes only with other restrictions.

steve

Thanks Steve.

This is something which has puzzled me since I first read about it, as the plumbing methods commonly used in the U.K. are rather different (not to mention very antiquated!). I saw the pipework when I was in the U.S., but never really traced it that closely.

I'm trying to visualize this "wet venting" system. Would this be something along the lines of taking a pipe upward from a fixture on the first floor and using that as the actual drain line for a second-floor appliance?

So there would then be a vent pipe from the second-floor trap, but the first-floor appliance effectively uses the drain from the second-floor appliance as its vent?

Paul, you are correct with your description of a wet vent. The UPC only allows fixtures on the same floor level to be wet vented. The section of pipe being used as a wet vent shall not exceed 6' in length and that section shall be one pipe size larger than required, for the drain(s) of the fixture(s) that are draining into the wet vent. Only one and two fixture unit fixtures can be drained into the wet vent.

The larger size makes sense. I recall reading about the "unit" designations now. Isn't it something like 1 unit for a lavatory basin, 2 units for a bathtub and so on?

I don't suppose you have any links to sites which might give a good general outline, maybe with some diagrams?

Paul: Once I get my scanner to start working again (should be shortly) I'll post or e-mail you some isometric drawings for DWV systems (Drain, Waste and Vent). You will be surprised at just how little venting is actually required under the International Plumbing Code. We used to use the Uniform Plumbing Code (many states still do) but not anymore. In my state, a plumber must know how to utilize the allowances offered by the Int. plumbing code or that plumber will not win the bid.

Ryan,

Thanks -- That would be appreciated.

There is very little venting employed in the average home drainage system here. The single-stack system just takes the main stack up to vent above roof level, and the individual drain lines just connect straight into it with no separate vent pipes from behind the the traps.

It's still common for even new homes to use the old system where drain lines on the ground floor don't actually connect directly into the main pipework. The pipe just runs outside and discharges over a gully, the latter having its own trap before connecting into the sewer line.

Some old properties still have a system where this approach is used for second-floor appliances as well. The bath and basin pipes discharge into a kind of hopper at just below second-floor level, and then a pipe runs down the outside of the house from there to the main drain.

Water supply systems can be just as "primitive."

Like a water tank in the loft?

Yes! I'm sure that some people would never bathe in the water that comes from these again if they could see the stuff that finds its way in there.

Paul:

As was mentioned, there are differing codes throughout the US. I just learned about a difference between the plumbing codes in New York and New Jersey. A neighbor who is originally from New York did a bunch of plumbing work in his house. Turns out that the sewer/vent setup was not up to the NJ codes. In NY, a 4" pipe is used for the sewer line, and it extends up through the roof. In New Jersey, the sewer pipes (3") must have an additional 2" pipe specifically for venting. Apparently, the waste knows to stay in the 3" pipe and the gases know to stay in the 2" pipe, or something like that.

Anyway, he had to make a bunch of new holes, add joints, etc. to clear it up.