Backwater Valve Required?

[Tuttles Revenge]

I have a project where we installed plumbing for a detatched dwelling unit connected to the sewer of the house and extending to the street. This sewer and 3 nearby homes are above the highest manhole. My inspector is asking for a backwater valve but I don't want to install one. The wording of the code indicates that any plumbing on a floor located below the upstream manhole should be protected by a BWV. Without that present, is it necessary/required? The main house has plumbing lower than the the plumbing all located on the 2nd floor of the DADU, so regardless of having the new plumbing protected, they would get soaked.

Project is located in Seattle so UPC applies.

710.1 Backflow Protection Fixtures installed on a floor level that is lower than the next upstream manhole cover of the public or private sewer shall be protected from backflow of sewage by installing an approved type of backwater valve. Fixtures on such floor level that are not below the next upstream manhole cover shall not be required to be protected by a backwater valve. Fixtures on floor levels above such elevation shall not discharge through the backwater valve. Cleanouts for drains that pass through a backwater valve shall be clearly identified with a permanent label stating "backwater valve downstream."

 

[Tuttles Revenge]

So.. Finally got this resolved.. Because the code doesn't take into consideration a scenario where there may not be an upstream manhole cover they failed to write any rule. So in my case I emailed a copy of the sewer diagrams that showed no upstream MH cover to my inspector and he signed our final plumbing inspection. Still a gray area IMO.

 

[Sponsor]

 

[Terry]

You normally see issues like that near the lake where they are at the end of the line. I have heard a few stories about basements being flooded by the uphill homes. Seems to me that means a pump has failed or the sewer line needs work. My brother in law used to go down in the pits and work on those pumps.

 

[Tuttles Revenge]

This was in Lake City ish and on a steep hill. Lots of sewer lines above, just that this road had a stub line. Oddly enough, the neighbors house had once been owned by Jay Frees.. which was the name of a company I worked at located on Capitol Hill. Another aside, a house I remodeled on Lake Washington that drained into the pumped system, the owner was a diver and mentioned being able to see some of that underwater sewer system.

 

[hj]

The "upstream" manhole is referred to because it would be a "relief" point in the event of a downstream stoppage. If it does NOT exist, then the reference point would be somewhere upstream where the backflow COULD escape, and YOUR plumbing would have to be above that point NOT to need a backwater valve. Your inspectors were incorrect and your drawing should have told them that you MAY have needed one, regardless of the absence of an "upstream manhole".

 

[Terry]

Another aside, a house I remodeled on Lake Washington that drained into the pumped system, the owner was a diver and mentioned being able to see some of that underwater sewer system.

When my father was on the Metro planning council, they decided to install the sewer systems which cleaned up Lake Washington. Before they did that there were a lot of people that wouldn't swim in the lake. For water tag it was interesting. You could swim down a few feet and nobody could see you. Then the lake was cleaned up and visibility returned. Not all the way to the way it was in the 40's, but much better.

 

[Tuttles Revenge]

HJ. I believe that my interpretation and that of the inspector are actually correct. Letter of the law.

Spirit of the law maybe not. But the reality is their entire property would need to be protected by a normally open BWV in order to be truly protected because their entire house is below... perhaps they have some downspouts that could act as relief.. but then how would the upper portions of their 100 yr old house be separated? We run into this a lot in Seattle. I try to CYA as much as possible by sticking to the rules... but when costs and inconvenience get too high, and the homeowner doesn't want to pay for that, we ask for a waiver from the code from the chief inspector.. in this case the inspector signed off..