I have a super old house and I need to install a garbage disposal. Electric is already in place, just need to know how to do the drain. The existing plumbing is an S-trap. Do I need to convert to a P-trap, and how? Tailpiece and pipes are metal. I have a dishwasher as part of this as well. Inlets are all copper. House was built in 1840.
Garbage disposal installation in old house
- Thread starter dspahn
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P traps are the standard.
When you say, "Tailpiece and pipes are metal." and " Inlets are all copper.", are you saying the drains are copper as well?
Are you installing the garbage disposal in a single bowl sink or a double bowl sink? That will make a difference in how to convert the S-trap to a P-trap.
Are you installing the garbage disposal in a single bowl sink or a double bowl sink? That will make a difference in how to convert the S-trap to a P-trap.
It would be easier with pics
Wow, for some reason I did not see notifications on this thread. Thanks for all the replies! It is a single bowl, the drain in the picture shows a PVC sleeve, but the plumbing below is copper (yep- the drain is copper, not just the supply lines). I believe S-traps are out of code here, so I am planning to install a garbage disposal, and at that time switch the plumbing to a P-trap. Not sure if there is anything special to making that change. I have a lot of space to work with though! Any thoughts or special considerations I should factor in?
Pull that escutcheon up at the bottom of the drain pipe so I can see what type pipe is there.
Be aware that if you do this and the drain is worn enough it may start a leak.
Your dishwasher drain hose should be secured high up near the cabinet top bottom. I like drilling much hole for the dishwasher drain hose in the top of the cabinet sidewall to enter the sink cabinet. This way there no strap and no way for it to come down. It’s called the high loop method, some codes allow it, some don’t. I personally wouldn’t have it any other way.
Be aware that if you do this and the drain is worn enough it may start a leak.
Your dishwasher drain hose should be secured high up near the cabinet top bottom. I like drilling much hole for the dishwasher drain hose in the top of the cabinet sidewall to enter the sink cabinet. This way there no strap and no way for it to come down. It’s called the high loop method, some codes allow it, some don’t. I personally wouldn’t have it any other way.
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I would say your ''need'' for a garbage disposal is fooloish in the super old house. If you ''need a disposal'' because all the junk you put down the drain, you are putting too much BS down the drain. Just my opinion.
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Why exactly does the hose ''have to strapped up high", I understand this is code, but a useless practice with modern dishwashers.
I can concur with this message at least in the case of my particular LG dishwasher as I had the back off the unit and the drain hose assembly already has a built-in "high loop" that peaks at nearly the top of the unit itself.
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correct
Ludington
Well-Known Member
I never could figure that out, if your dishwasher has that high loop built in, you essentially have a built in trap. And the hose could get connected anywhere. You would not need another trap in the line. As the washer is never going to push all of its water through it and there will Always be a water block to stop any smells. (Not code, but it would be fine)
The "code" probably has more inertia built into it than most policies or guidance and is outdated in many areas.
The design of some dishwashers have that final caution statement taken care of just in case........... My internal-to-the-design high loop tops out at 33" above the floor.
What happens if the sink drain is stopped up and the sink is full of water and the little POS check valve integral to the dishwasher is fouled and doesn’t seal, like they do ?
AND
There’s no high loop or an air gap.
AND
There’s no high loop or an air gap.
I’ve had service calls where the repair was to move the dishwasher connection to the house side of the trap because of sewer gas smells.
Thats all I have for you guys, it’s up to you how you install your equipment.
Ludington
Well-Known Member
I'm sure my setup is very unconventional, my washer is to far from the sink to run the discharge hose to it. So I have added a high loop where at the top of the loop there is an air vent that leads to the normal sink vent stack. But then the drain line continues down and through the floor where it connects to the sink drain line. So the washer will push its water through its own high loop down to floor level then back up to my high loop and back down through the floor. Essentially creating a trap between the 2 high loops. But with the added air vent so no siphoning can occur. Certainly against code, but it does work.
Agreed. In that case I wouldn’t attempt to run the dishwasher and would have to call a plumber. I am not sure if my POS LG has a check valve in the line but I could be wrong.
I’d love to see a picture of how that connects. Sounds interesting with a vent between the dishwasher and the drain.
If it doesn’t have a check valve then it’s susceptible to backflow from the sink if it doesn’t have a high enough loop or an air gap.
Without a check valve it would be the same as a failed check.
