Washer drain odor when dumping

[redhooker]

Putting this in the general fifth wheel since it may be similar across different brands. We have an XLR thunderbolt with the washer prep in the garage. The washer is a straight drain, it does not pass through any tank. The problem is if the drain pipe is left open, every time you dump all of this fumes come barreling up the pipe and push the stench throughout the coach.

We have solved the problem by capping the drain. But the thought occurred to me, what if we want to install a washer? With those same fumes be pushing up through the washing machine drain?

Anyone else have a straight plumbed drain from the washer with a similar issue? Or was this a feature just used on the Thunderbolts?

[SailorSam20500]

Thinking that the drain is PVC pipe, you might think about putting in a HepvO valve. It might work...


https://www.rvtravel.com/much-better-p-trap/

[redhooker]

It is ABS pipe (should still work), and I have thought of that but wanted to know if anyone that has installed a washer has had issues before I take a sawzall to the wall to install something.

[nomad297]

A HepvO is a terrible choice if you intend to ever use it for a laundry drain. Way too much stringy garbage comes from clothes washers and will hang up and collect in the beak of the HepvO causing it to allow the sewer gases to escape. A traditional p-trap is your best option here.

I don’t understand what you mean by a “straight drain” that does not pass through the tank. Can you explain?

Any drain should have a p-trap, unless yours already has a HepvO on it. If you aren’t using this drain and it has a p-trap, the p-trap has either never had water in it or the water has evaporated allowing the gases to flow freely into your RV. Since you aren’t using it now, you have done the right thing by capping it — why leave it open if you’re not using it? If you don’t cap it, you will have to occasionally put about a pint of water in the drain to keep the trap full of water and sealed.

Bruce

[rjshiflet]

Our washer drain (which we do not use) is capped with a PVC or ABS "stopper" of sorts. I have also heard of people simply wadding up a piece of an old towel and shoving it down the drain to block the smell if no washing machine is present.

[redhooker]

Originally Posted by nomad297

A HepvO is a terrible choice if you intend to ever use it for a laundry drain. Way too much stringy garbage comes from clothes washers and will hang up and collect in the beak of the HepvO causing it to allow the sewer gases to escape. A traditional p-trap is your best option here.

I don’t understand what you mean by a “straight drain” that does not pass through the tank. Can you explain?

Any drain should have a p-trap, unless yours already has a HepvO on it. If you aren’t using this drain and it has a p-trap, the p-trap has either never had water in it or the water has evaporated allowing the gases to flow freely into your RV. Since you aren’t using it now, you have done the right thing by capping it — why leave it open if you’re not using it? If you don’t cap it, you will have to occasionally put about a pint of water in the drain to keep the trap full of water and sealed.

Bruce

Thanks for the heads up on the hepvo. By “straight pipe” I mean the washer is plumbed directly to the 4” main drain line leaving the coach. No gray tank or black tank to pass thru you MUST be connected to sewer if you want to use the washer. When you dump the black or gray tanks air is forcefully pushed up the washer drain-we used a gallon ziplock bag zip tied over the pipe to stop the stench when dumping and it inflates like a ballon.

My question is if anyone else has a washer drain like ours and actually uses it are there any difficulties sealing the drain when you hang the washer drain in this pipe? Hard plumb? Will the pint of water in the trap stop this large rush of pressurized funk?

This camper has other plumbing design flaws such as the rear half bath black tank is vented via a wye just behind the sink p-trap. Therefore “tapping” into the sink vent ala’ redneck engineering. This means if you run the sink more than 20 seconds or so the toilet violently burps when flushed (even an hour later-a real ticking time bomb) splashing all the walls. Forest River should take note if they see this and adjust future plumbing accordingly.

[rockfordroo]

I've never heard of a washer being plumbed directly to the sewer outlet.

Your plumbing doesn't sound right to me. Might want to wander into the dealers and look at another unit like yours and see how it's plumbed.

If still under warranty, have it re-plumbed.

[nomad297]

It is odd (or a new thing) that your laundry connects directly to your tank discharge line. Are you sure that you don’t have a separate gray water holding tank dedicated to just the laundry with its own dump valve that you haven’t yet discovered? This wouldn’t be the first time that somebody discovered a dump valve they weren’t aware of until asking questions here.

First things first: have you ever put water into your laundry drain to fill the trap that should be there? If not, do this and your problem will probably be solved. Then, once you do start using that drain regularly with a washer, you should have no problems. Just leave it capped or plugged until you do start using it. If you have done this and you continue to get gases escaping, you need to investigate the venting.

As I said before, every drain is supposed to have a trap, and if that trap is full of water it is impossible for the gases to enter your RV. If there is a trap, first make sure it has water in it. If you can’t tell if there is a trap or if the trap is filled with water, or not by looking, then listen. Listen at the opening where you would put the washer hose. If you can hear water running here when you are draining something else, there is either no trap or the trap is dry. If there is a trap, but it is dry, fill it with water. If the trap isn’t properly vented, it can be sucked dry when you dump your tank — especially if the drain is connected directly to the 3” portion between your tank and the dump valve as you describe — a lot of suction is created here when the tank is dumped. If there is a trap and it is full of water, listen again as somebody else dumps the tank. If it isn’t properly vented, you will most likely hear a gurgle at the laundry drain opening as the water is sucked out of the trap, then you will smell the gases. If this happens, there is either no vent or the trap is not sufficiently vented. The standard air admittance valve that is ubiquitous in RVs and probably installed on your laundry drain is only sufficient for 6 DFUs (Drainage Fixture Units) on a branch and may not be allowing enough air into the drain between the trap and the 3” drain. While this air admittance valve should be sufficient for a laundry drain, it may not be in your case. Step it up to an air admittance valve that will allow 20 or more DFUs on a branch. This will allow more air to enter the drain when you dump the tank and hopefully stop the trap from getting sucked dry.

Your half-bath problem is due to the absence of an atmospheric vent to your tank. Either there is no vent through the roof for the tank or there is a vent through the roof and it is pushed too far into the tank or otherwise blocked. If it is pushed too far into the tank, as soon as the level of water in the tank reaches the bottom of the vent, the vent will no longer allow displacement of air from the tank to atmosphere. An air admittance valve is not a substitute for an atmospheric vent. An air admittance valve only works in conjunction with an atmospheric vent — you cannot vent any tank with just an air admittance valve — the air admittance valve will allow air to go into the tank, but it will not allow air to go out — you must have a vent to atmosphere from the tank to allow displacement of the liquids going into it.

I know I have covered a lot of things here, but I haven’t touched on a lot of other things. I will wait for questions and answers from you and opinions from others before I end-up writing a whole book.

Bruce

[redhooker]

No, there is no warranty issue.

This washer is intentionally plumbed this way by Forest River on all garage washer hookups. Many a Thunderbolt owner (according to the dealer) has learned the hard way trying to wash clothes not connected to a sewer.

Bruce, there is no missing vent. The rear black tank is vented THROUGH the sink drain (to save time on the assembly line) and up the sink vent. Intentionally. So running the sink builds pressure in the black tank. It is a faulty design unfixable at this point unless I want to run a new vent pipe through the living room.

All these items are without question. I have had almost the entire chloroplast underbelly off the coach and visualized everything.

Thanks for the replies they are appreciated, back to my question. Anyone else have a washer plumbed like a Thunderbolt?

[nomad297]

Originally Posted by redhooker

Bruce, there is no missing vent. The rear black tank is vented THROUGH the sink drain (to save time on the assembly line) and up the sink vent. Intentionally.

If this is the case, there is nothing wrong with the way it is done. It’s not even cutting corners. As long as the sink vent goes through the roof and the sink drains into the black tank, the tank is vented to atmosphere. I suspect here that the vertical portion of the sink drain below the tee (which is now a wet vent for the tank) for the trap arm is protruding too far down into the black tank and as soon as the water gets deep enough in the tank to cover the bottom of the sink drain, you lose your vent, then pressure builds in the tank.

Bruce

[rockfordroo]

Originally Posted by redhooker

No, there is no warranty issue.

This washer is intentionally plumbed this way by Forest River on all garage washer hookups. Many a Thunderbolt owner (according to the dealer) has learned the hard way trying to wash clothes not connected to a sewer.

Bruce, there is no missing vent. The rear black tank is vented THROUGH the sink drain (to save time on the assembly line) and up the sink vent. Intentionally. So running the sink builds pressure in the black tank. It is a faulty design unfixable at this point unless I want to run a new vent pipe through the living room.

All these items are without question. I have had almost the entire chloroplast underbelly off the coach and visualized everything.

Thanks for the replies they are appreciated, back to my question. Anyone else have a washer plumbed like a Thunderbolt?

Would have been nice if you'd said all this in your first post.

[redhooker]

Originally Posted by rockfordroo

Would have been nice if you'd said all this in your first post.

I did-here is my first post (note the questions at the end):

Originally Posted by redhooker

Putting this in the general fifth wheel since it may be similar across different brands. We have an XLR thunderbolt with the washer prep in the garage. The washer is a straight drain, it does not pass through any tank. The problem is if the drain pipe is left open, every time you dump all of this fumes come barreling up the pipe and push the stench throughout the coach.

We have solved the problem by capping the drain. But the thought occurred to me, what if we want to install a washer? With those same fumes be pushing up through the washing machine drain?

Anyone else have a straight plumbed drain from the washer with a similar issue? Or was this a feature just used on the Thunderbolts?

[redhooker]

Soooo...

I just wanted to know:

If anyone else can reply that has a washer plumbed like this. When dumping a full tank it blows a lot of pressure up the washer pipe and I am not sure a pint of water in a P trap will hold it. It inflates a gallon bag hard when dumping a full tank up front.

Yes it sucks the washer is plumbed like that. Just the way it is though.

The sink in the half bath issue is not in need of suggestions or repair. Just mentioned it as a related frustration. The sink drains down both the drain pipe as well as the black tank vent pipe causing a pressure build in the tank. That burp exits the toilet upon flushing. I have owned a dozen or more RVs-never had a black tank vent zig zag into a sink drain line right behind a P trap. So in my opinion it is indeed cutting corners.

[nomad297]

Originally Posted by redhooker

Soooo...

I just wanted to know:

If anyone else can reply that has a washer plumbed like this.

What you are asking about is not RV-specific. What you are experiencing and describing applies to any drain, waste and vent system.

To answer your question about whether or not the water in the trap will prevent the gases from pushing through the washer stand pipe: it should. You can test this by using the bag that you have already placed over the drain — this is actually the exact same way plumbers determine what is going on when working-out venting problems in non-RV related situations. Once the trap is full of water, put the bag back on top of the stand pipe and secure it with a rubber band, leaving room in the bag so you can see if it gets sucked into the stand pipe or if it fills like a balloon. If your trap is holding its seal, the bag will either not move at all or it will get slightly sucked in, then slightly fill as the water in the trap bobs up and down from the air movement in the pipe between the trap and the top of the stand pipe. If the bag looks the same as it did when you started this test, the trap is probably still sealed. If it remains sucked into the stand pipe, the trap was probably sucked dry. Once it has become sucked dry, there is a clear path for the gases to escape from the stand pipe. If it has been sucked dry, you need to work out a way to vent it properly so water remains in the trap when you dump.

If the trap is vented properly with an air admittance valve and the rush of water and air created when you dump your tank causes gases to push past the laundry trap and out of the stand pipe, you need to explore why the flow of water is being restricted between your dump valve and the end of your sewer hose. With an air admittance valve, the only reason air will push back up into the laundry drain in your situation is because there isn’t sufficient flow beyond your dump valve — the huge amount of water being released from your tank completely fills the 3” waste pipe and the sewer hose, so there is no longer a space of air at the top of these pipes which first creates positive pressure in the laundry drain, then negative pressure as the flow slows down. This can cause your laundry trap to get sucked dry.

Dumping a tank in an RV Can cause problems similar to when a large volume pump discharges into any DWV system. Wherever a pump branch discharges into the main drainage system, the pipe it discharges into is at least one pipe-size larger than the pump branch to prevent the pressure and suction I am talking about. With an RV, this method of pipe sizing is not followed, so it is more likely to be a problem with an RV than with a standard building’s plumbing system.

Now, what could be restricting the flow after the dump valve? Many people like to create a trap in their sewer hose before it enters the campgrounds sewer. Many people just lay their hose on the ground with no slope from the dump valve to the sewer inlet. Both of these things will cause the flow to slow considerably, especially the trap in the hose, or a hose that is not sloped all of the way to the sewer inlet. Even with slope on the hose, if you make a trap in the hose, it will slow the flow and create pressure that can push air back towards the laundry drain.

I really think you have nothing to worry about once you start using your laundry drain, but if you do, you just need to work out a way to prevent the laundry drain trap from being sucked dry by venting it properly (including what I mentioned about the sewer hose). I doubt there will be enough air pressure created when you dump your tank to push it beyond the water in the sealed trap.

I have more to explain, but I have run about of time and I have to get to work.

Bruce