Help with laundry room plumbing

Ramjam · Mar 4, 2014

The plumbing in my laundry room seems to be missing a vent, or there are too many P-traps.

The current setup is this:
The sanitary line that goes to the laundry room connects to my main sanitary line while it is horizontal. The line going to the laundry room is 1 1/2 inches. Immetidately on the line there is a p trap. This trap is vented about 2 feet downstream with the main vent for the house going through the roof.

The pipe going into the laundry room runs about 14 feet horizontally, then there is a tee which goes to the laundry sink. The other side of the tee goes to the standpipe for the washing machine. The standpipe does not have a P trap. It has a 90 degree bend that sends it vertical.

The sink has it's own P trap. It is not vented.

My options are either to eliminate the P-trap on the sink, leaving only the trap 14 feet down the line, or leave the trap on the sink, add one to the standpipe, and add a cheater vent. Which option is better?

Also, I'd like to add a cleanout to this line. Where would be the best place for this?

Thanks!

Terry · Mar 4, 2014

The best place for a cleanout goes is at the end of the line. Within five of the ends works in some cases.

The washer and the sink should have a vent. A 2" trap arm can go 60" before the vent, and 1.5" can go 42"
Having a running trap in the line 14 feet downstream doesn't do anything.

Sponsor · 2022-01-29T12:20:58-0800

Ramjam · Mar 4, 2014

Terry said:
The best place for a cleanout goes is at the end of the line. Within five of the ends works in some cases.

The washer and the sink should have a vent. A 2" trap arm can go 60" before the vent, and 1.5" can go 42"
Having a running trap in the line 14 feet downstream doesn't do anything.

can you explain when you say the trap doesn't do anything? I would've thought it would stop the sewer gasses in that whole system.

Regardless, am I better off putting a trap on the sink and standpipe? and since it's a 1.5'' line, if I put the cheater vent within 42'' of the furthest trap I should be ok?

Thanks!

Terry · Mar 4, 2014

can you explain when you say the trap doesn't do anything? I would've thought it would stop the sewer gasses in that whole system.

That trap will siphon as there isn't an air break anywhere near close enough.

If you have have siphoned water with a hose, you will know that lifting the hose for even a second stops the siphon. An open vent needs to be near enough to the trap, so that the pipe is not full of water at that point. With a 1.5" pipe, that distance 3'-6"
This is very old science turned into working methods of plumbing. Plumbers didn't invent fluid dynamics, but we use it.

Without a sketch of your intention, it's hard to say if you plan on doing it right.

Terry · Mar 4, 2014

can you explain when you say the trap doesn't do anything? I would've thought it would stop the sewer gasses in that whole system.

That trap will siphon as there isn't an air break anywhere near close enough.

If you have have siphoned water with a hose, you will know that lifting the hose for even a second stops the siphon. An open vent needs to be near enough to the trap, so that the pipe is not full of water at that point. With a 1.5" pipe, that distance 3'-6"
This is very old science turned into working methods of plumbing. Plumbers didn't invent fluid dynamics, but we use it.

Without a sketch of your intention, it's hard to say if you plan on doing it right.

hj · Mar 5, 2014

If you put a trap on the washer pipe, neither the washer or sink will drain proper, if at all, and a cheater vent will not help it either. You have to remove the existing trap, assuming what you describe is what I am interpreting correctly, then install a washer trap and vent. Actually, because of where the sink is located, you need the vent to be on the sink drain, regardless of whether or not you have one on the washer connection. As a side note, that 1 1/2" line is probably inadequate for a washer drain line.

Ramjam · Mar 5, 2014

Terry said:
That trap will siphon as there isn't an air break anywhere near close enough.

The trap that is 14 feet away is vented about 2 feet past it. The one for the sink does not have a vent. I can either add one or remove the P trap at the sink and just run a 90. The standpipe currently only has a 90, I can add a trap there as well if required. I would rather have a trap under the sink though so I think I will add a trap to both the standpipe and the sink and add a vent within the required distance.

I realize it might not be ideal, but is it ok to have two vented traps on the same line, one being under the sink/standpipe and one 14 feet down on the same line? I will try to make a drawing, but I'm not the greatest at that by any means. The answers to the above questions would really help me out though.

I appreciate your time.

Ramjam · Mar 5, 2014

Here is my best attempt at drawing out the plumbing. The top picture is the start of the run, it continues onto the bottom picture after the horizontal pipe does a 90 degree turn, continuing horizontally. Again, I figure my options are to either remove the p trap from the laundry tub, leaving the one P trap on the line at the start, or to add a P trap to the standpipe, leaving the p trap on the sink and also the one further down the line, and add an AAV vent. What do you think?

Edit: I could also add a Y to the laundry sink line where it runs vertically, go up higher and put an AAV there, if that makes any difference. From my understand this would be a wet vent, but if I do that will it be enough to vent the standpipe trap also?

Terry · Mar 5, 2014

Remove the inline p-trap
Change pipe to 2"
Add a p-trap for the washer
Add a p-trap for the sink
Add a vent "above" the trap arm for the washer
Add a vent "above" the trap arm for the sink

Ramjam · Mar 5, 2014

Terry said:
Remove the inline p-trap
Change pipe to 2"
Add a p-trap for the washer
Add a p-trap for the sink
Add a vent "above" the trap arm for the washer
Add a vent "above" the trap arm for the sink

My problem is that I can't remove the inline P-trap at this time. It's something I can get to in a few months, but it will require a lot of work and money. Is there another solution I can use at least for now that includes leaving that inline P-trap? Anything at all?

For instance, if I do everything you say but leave the inline p trap, will it work until I can remove it?

Terry · Mar 5, 2014

For instance, if I do everything you say but leave the inline p trap, will it work until I can remove it?

That may work, but so far that p-trap in only hindering the plumbing. It isn't doing anything "for" the plumbing.

Ramjam · Mar 5, 2014

Terry said:
That may work, but so far that p-trap in only hindering the plumbing. It isn't doing anything "for" the plumbing.

I understand this. The reason I ask is because I'm currently working in the laundry room and would like to get this done before starting another project. Right now I can do everything you say, close it up, and the next project will be breaking concrete to be able to remove that P-trap. Until then though I want to make sure my washing machine will still function.

Ramjam · Mar 5, 2014

Would this work? Changing the stand pipe bend to a p-trap, and placing the vents in the locations (in red) marked in the picture?

MikePlummer · Mar 5, 2014

Ramjam said:
View attachment 23780

Would this work? Changing the stand pipe bend to a p-trap, and placing the vents in the locations (in red) marked in the picture?

no. Terry has given you good advice on how to pipe this...if you cant get at the running trap right away, at least pipe it the way Terry has shown and remove the running trap afterwards. it isn't the best way, but will be better in the long run. our code does allow you to have this pipe sized as 1-1/2", but it would be better practice to use 2" if possible.

hj · Mar 5, 2014

Where is that "P" trap that you have to "remove concrete"? If it is under the floor, then you have other problems that we have not addressed, because your drawings implied that it was above the floor. Leaving the trap where it is and doing ANY "upgrades" will create a "double trap" and that could prevent anything from draining. It would depend on whether the water would have enough force to push its way through the second trap.

Ramjam · Mar 5, 2014

mikeplummer said:
no. Terry has given you good advice on how to pipe this...if you cant get at the running trap right away, at least pipe it the way Terry has shown and remove the running trap afterwards. it isn't the best way, but will be better in the long run. our code does allow you to have this pipe sized as 1-1/2", but it would be better practice to use 2" if possible.

I will be doing exactly as you say. I can't switch to 2 inch as I would have to reduce it back to 1.5 to connect to the trap until I can take it out, which from what I gather is a code violation as well.

Ramjam · Mar 5, 2014

hj said:
Where is that "P" trap that you have to "remove concrete"? If it is under the floor, then you have other problems that we have not addressed, because your drawings implied that it was above the floor. Leaving the trap where it is and doing ANY "upgrades" will create a "double trap" and that could prevent anything from draining. It would depend on whether the water would have enough force to push its way through the second trap.

The trap is above the slab, but just above it. After cutting it off there isn't enough pipe to glue a new fitting on. Because of this I will have to cut the tee which is on the vertical line, however after doing this there won't be enough pipe to glue to. As a result I will have to break up concrete and replace a good portion of the underground pipe...

Terry · Mar 5, 2014

Maybe a picture of the offending santee.
We can often "split" off a fitting from the pipe, and reuse the pipe that it was glued to. To do that, we cut where the end of the pipe would be, cut on the hub, and taking a flat blade screwdriver and a hammer, pry it off the pipe by using the flatblade like a chisel.

Ramjam · Mar 5, 2014

Terry said:
Maybe a picture of the offending santee.
We can often "split" off a fitting from the pipe, and reuse the pipe that it was glued to. To do that, we cut where the end of the pipe would be, cut on the hub, and taking a flat blade screwdriver and a hammer, pry it off the pipe by using the flatblade like a chisel.

This is interesting. The santee is behind drywall, but that's not really a concern I can repair it easily. My concern of course would be breaking the pipe. Id be in big trouble then. That part of the pipe was glued together just over a year ago. Would that make it any easier or harder?

Also, using your drawing which is what I will be doing, is there a good spot for me to add a clean out?

Terry · Mar 5, 2014

Also, using your drawing which is what I will be doing, is there a good spot for me to add a clean out?

End of the line where the washer is.

Newly installed fittings and pipe tend to be easier to split apart. We take our time with that stuff. We don't like breaking concrete either.

Help with laundry room plumbing

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