Septic Tank P-Trap

[Steve_J_H]

Hello, I am renovating my own house, and am at the point of planning out the dwv system. We demoed everything and are relocating rooms and therefore all the plumbing fixtures as well. The "new" house will have 3 full baths, 1 kitchen, 1 washer. I am looking for advice on how to properly tie into my septic tank- from the wall there is a 4"steel p-trap, and an elbow that goes straight off to the side (this section was where the old vent was tied in, along with the kitchen and bathroom drains). In front of the trap is a sani-tee with a cleanout, where another bathroom was tied in, you can see the old pvc in the photo. My question is, can I plan my dwv system to drop into the sani-tee and consider that longer straight section obsolete? Or do I need to incorporate that straight section into the design?

 

[Reach4]

The common terms for that U-shaped trap you have there is building trap or whole house trap. In general, best practices now are to not have the whole-house trap, but to have the vertical to horizontal transition done with a combination (combo) tee or a (45 and a wye). The septic tank gasses go out the roof of the house.

HOWEVER, there are places where a whole house trap is not only permitted, but required. I don't know what the situation is for Syracuse, New York. I suspect they are now in the camp of not allowing it (but it could stay grandfathered). I suggest you ask your local code authorities about that. I did a couple searches, and did not find a reference. IPC does not permit it except for special cases.

 

[Sponsor]

 

[Steve_J_H]

The common terms for that U-shaped trap you have there is building trap or whole house trap. In general, best practices now are to not have the whole-house trap, but to have the vertical to horizontal transition done with a combination (combo) tee or a (45 and a wye). The septic tank gasses go out the roof of the house.

HOWEVER, there are places where a whole house trap is not only permitted, but required. I don't know what the situation is for Syracuse, New York. I suspect they are now in the camp of not allowing it (but it could stay grandfathered). I suggest you ask your local code authorities about that. I did a couple searches, and did not find a reference. IPC does not permit it except for special cases.

Thank you, I am not surprised that this is outdated technology. Do you see any potential risks in dumping all waste from a (properly vented) whole house system into the line before the building trap?

 

[Reach4]

Other than the possibility of clogs, which I think is the reason that whole house traps have mostly been done away with, no. I am not a plumber.

 

[WorthFlorida]

When cast iron pipe was king and homes started to add indoor plumbing, the whole house trap was used since old fixtures installed with drum traps, s-traps or no traps at all buy homeowners, they was a last defense from sewer gas. As the industry learned and standards were improved on, this type of trap was redundant. My parents house built in 1953 had cast iron trap just like yours and when the cesspool was removed and the house connected to the city sewer system (1975), it was eliminated.