Air-Admitance Valve

[jerryspark]

I have a 2020 Coachmen Leprechaun 260DS. Does anyone know where my air-admittance valve for the kitchen sink is located? Thanks for your help. Is this it?

[CC38EL]

That is the waterless sanitation valve....or the RV ''P" trap. Your air admittance valve should be higher up if you have one.

Or it may be in another sink area.

[BigHomey]

That is a HEPVO waterless P-trap, and an air admittance valve is not needed with it.

AL

[jerryspark]

I can pour 2 gallons of water in my kitchen sink, and when I add another gallon the sink starts to back up. I can let it sit like that for awhile and nothing happens. When I go outside and pull the gray water valve, I get a good rush of water and the sink drains.

[bubbles]

If the gray tank is vented properly you should not have that issue.

[nomad297]

Originally Posted by BigHomey

That is a HEPVO waterless P-trap, and an air admittance valve is not needed with it.

AL

The use of a HEPvO trap does not negate the need for a vent or an air admittance valve for proper venting of a drainage system.

If he removed that 1-1/2” 90 at the back, replaced it with a 1-1/2” sanitary tee and added an AAV to the top of the sanitary tee, then installed a new HEPvO trap (since the existing HEPvO trap will be toast) or a standard trap, he wouldn’t be having the problems he’s having.

EDIT: AAVs cannot be used in place of an atmospheric vent. There must still be an atmospheric vent on any drainage system for the AAV to work properly.

Bruce

[nomad297]

Originally Posted by bubbles

If the gray tank is vented properly you should not have that issue.

Maybe, maybe not, but it does sound like it isn’t vented. If the tank is not vented, the AAV will not help, but if it is vented, the AAV will solve his problem.

Bruce

[cboss]

The valve looks like this.

[jerryspark]

I have not able to locate that vent yet. The sink worked fine last year and few weeks ago while we were camping. I just noticed the problem this week when I was running water to freshen it.

[bubbles]

Originally Posted by nomad297

The use of a HEPvO trap does not negate the need for a vent or an air admittance valve for proper venting of a drainage system.

If he removed that 1-1/2” 90 at the back, replaced it with a 1-1/2” sanitary tee and added an AAV to the top of the sanitary tee, then installed a new HEPvO trap (since the existing HEPvO trap will be toast) or a standard trap, he wouldn’t be having the problems he’s having.

EDIT: AAVs cannot be used in place of an atmospheric vent. There must still be an atmospheric vent on any drainage system for the AAV to work properly.

Bruce

In the HEPvO installation they show and claim that for new (first time) installs the typical vent is not required. They do say that modifying existing plumbing to the HEPvO configuration all existing vents shall be retained. Good or bad, I don't know. Not saying that the additional local vent would not fix problem but because this a new unit the HEPvO should have been installed as per instruction provided for the plumbing which eliminated the P trap and local vent requirement.

[CC38EL]

Looking at your floorplan, it would seem that, if you don't have an air admittance valve in your bathroom sink area or under your kitchen sink, then you may need to get on your roof and find the vent for the grey water tank. It may be plugged somehow.

Does this happen all the time? Even when the tank is empty? If so, you have a venting problem.

If it only happens when you have a half full or more tank level, you may have an issue with the vent pipe being too far into the tank.

I had that issue with a black tank once. As the tank filled, it covered the vent. As the tank filled further, it pressurized the tank. My wife found the issue when she went to flush.....and it went up instead of down. Fortunately for me, it was number 1. It could have been much worse.

[Scrapper]

Another thing to check is the vent cap if you have a slow draining grey tank, kitchen, sink or shower. We had the problem 6 yrs ago and found a hornets nest in the vent cap.

I have two vent stacks on my tt. One for the black tank and one for the grey tank. Both my shower and kitchen sink have p-traps and are connected with same down drain pipe to the grey tank. The grey tank vent also serves the shower and kitchen sink via sanitary 'T' near the sink. My bathroom sink drained fine as it has a p-trap and AAV, the drain pipe runs across the floor to a 'T' connected to the same down pipe going into the grey water tank.

[nomad297]

Originally Posted by bubbles

In the HEPvO installation they show and claim that for new (first time) installs the typical vent is not required. They do say that modifying existing plumbing to the HEPvO configuration all existing vents shall be retained. Good or bad, I don't know. Not saying that the additional local vent would not fix problem but because this a new unit the HEPvO should have been installed as per instruction provided for the plumbing which eliminated the P trap and local vent requirement.

You are correct. The main purpose of an individual vent (whether it is atmospheric or an AAV) is to keep a standard trap from siphoning, and with the way a HEPvO trap is designed, this is not an issue, but an individual vent can also serve as a vent for an entire system when it is incorporated into a wet vent design. My suggestion for the installation of an AAV in this situation was just as a hit-or-miss attempt of solving the problem, but more information has been provided by the OP since I wrote what I did and I now doubt that adding an AAV here would help.

In what I wrote I was assuming his system had the required atmospheric vent that all gravity drainage systems need to flow. You might get away without an atmospheric vent in some situations, but with a small self-contained system such as with what we all have in our RVs with holding tanks, an atmospheric vent is absolutely necessary. Whether the vent connects to just the tank and goes to atmosphere or if it just extends from one drain at one fixture and goes to atmosphere, it doesn’t matter — either way, there must be an atmospheric vent to allow displacement of the air in the system when fluids are introduced. Ideally, there would be one vent from the tank to atmosphere and at least one more on the drainage system, but if there is a vent to atmosphere from the tank or just one somewhere in the drainage system, an AAV should not be necessary for the HEPvO trap to work properly.

Assuming that the OP’s system does have the required atmospheric vent somewhere, I suggested installing the AAV because sometimes odd things happen with drains and they can lock water for several different reasons, so the introduction of air from the AAV where I suggested might have solved the problem.

However, somewhere after the post of mine that you quoted, the OP stated that this is a new problem and this sink once drained properly. I wasn’t considering this when I wrote what I did and this changes everything. It now sounds like he probably does have an atmospheric vent and it is probably blocked, maybe with a wasps nest like somebody else suggested or something similar.

Bruce

[robin97405]

We are having the same problem but can’t find the vent on the roof — ours is a Leprechaun 298 KB, did you find the vent?

[nomad297]

On Monday I went to a clogged kitchen sink call. Nothing unusual except the drainage system for the kitchen was very new (in an old house) and was run entirely with 2” PVC — about a fifty-foot run from the kitchen to where it connected to a 3” stack. I could see the entire run in the basement and the slope was good. It was just odd that such a new drain would be completely clogged already. I ran a 5/8” cable with a 1-1/2” grease cutting head the entire length. When I pulled it back there was very little grease on my cable and no evidence of anything that could be causing the stoppage. I put all of the under-sink drains back together and started to run the faucet, only to find out the line was still clogged — I hate it when this happens. I took it all apart again, snaked again, put it back together again and got the same result. That was a lot of work to do with no results. I knew there had to be something that wasn’t right.

I began to investigate venting issues because there was no way the drain wasn’t clear by now. I noticed a heat/ac transfer/return register about seven feet up on a wall about five feet away from the kitchen sink — it was an odd place for something like this to be, so I took the cover off and inside, in the wall, was a vertical 1-1/2” PVC pipe with an air admittance valve on top of it. When this kitchen was remodeled, whoever did the plumbing abandoned the original atmospheric vent and replaced it with this rig using an undersized vent pipe with an undersized (junky black one like we have in our RVs) AAV. I removed the AAV and shook it and the rattle I could hear told me the spring in the AAV had failed. With the AAV removed, I filled the kitchen sink with water, pulled the plug and it drained like a bandit. All of that snaking I did was probably for no reason. There was nothing I could do about the undersized vent without demolishing the kitchen, so I just installed a larger DFU AAV (Studor brand) on the existing pipe, put the register back on and I was done.

The point here is, even though this kitchen drain is connected to the 3” stack fifty feet away, and that 3” stack continued up through the roof as the main atmospheric vent for the entire drainage system, the kitchen would not drain without its own individual vent or AAV in close proximity to the kitchen sink. Even though this particular vent wasn’t installed properly, it was still necessary (and worked) to allow air to enter the 2” kitchen drain for the water to flow. This is why I suggested the OP might want to try adding an AAV to just see if that does the trick. It might just work.

Bruce