New RV kitchen sink won't drain unless all waste water valves are open

fullernj

Member
We bought a 2020 Elkridge 38MB less than 2 weeks ago and have been having trouble getting the sink in the island to drain. It works for a while, then starts to drain slowly, then not at all. We have been doing some troubleshooting, and have replaced the air admittance valve, twice, just in case. The p-trap has been taken off and it is perfectly clean and new. We have snaked the drain under the sink all the way to the tank, as well as snaked the roof vent, with no effect. I used a shop-vac to suck out the gray tank from the bottom to see if there was a clog there, and it worked for about an hour. We have tried to keep the grey tanks closed to see if the sink will continue to drain, no luck. The only solution that keeps the kitchen sink draining is to keep all 3 waste valves open, including the black. This is not an acceptable solution, and I need some ideas about what might be going on.
 

danemayer

Well-known member
Hi fullernj,

Welcome to the Heartland Owners Forum.

Is the p-trap under the sink a conventional p-trap? On some builds, a HepVo valve is used, as pictured below.

Also, if you remove the air-admittance valve completely, does the sink drain?
 

Attachments

  • HepVo valve.jpg
    HepVo valve.jpg
    26 KB · Views: 49

fullernj

Member
Hi fullernj,

Welcome to the Heartland Owners Forum.

Is the p-trap under the sink a conventional p-trap? On some builds, a HepVo valve is used, as pictured below.

Also, if you remove the air-admittance valve completely, does the sink drain?

It's a conventional p-trap. When the problem first started, loosening the air admittance valve helped, so we replaced it completely. Now loosening it, and removing it does not help at all, still no draining.
 

danemayer

Well-known member
You've done just about everything I can think to check. The only thing you didn't mention is between the sink and the p-trap. But you probably checked that while the p-trap was off.

On our floorplan, the drain coming out of the kitchen island goes through a horizontal run under the floor before it empties into the gray tank. If that horizontal pipe isn't actually horizontal, I suppose it could impede proper drainage. In that vein, when the p-trap is removed, can you pull up on the drain pipe that goes through the floor?
 

SLO

Well-known member
We bought a 2020 Elkridge 38MB less than 2 weeks ago and have been having trouble getting the sink in the island to drain. It works for a while, then starts to drain slowly, then not at all. We have been doing some troubleshooting, and have replaced the air admittance valve, twice, just in case. The p-trap has been taken off and it is perfectly clean and new. We have snaked the drain under the sink all the way to the tank, as well as snaked the roof vent, with no effect. I used a shop-vac to suck out the gray tank from the bottom to see if there was a clog there, and it worked for about an hour. We have tried to keep the grey tanks closed to see if the sink will continue to drain, no luck. The only solution that keeps the kitchen sink draining is to keep all 3 waste valves open, including the black. This is not an acceptable solution, and I need some ideas about what might be going on.

Can you post a pic. Especially include a pic of the air admittance valve in relation to the trap and and how high it is above the bottom of the sink.


Sent from my iPad using Tapatalk
 

Flick

Well-known member
We bought a 2020 Elkridge 38MB less than 2 weeks ago and have been having trouble getting the sink in the island to drain. It works for a while, then starts to drain slowly, then not at all. We have been doing some troubleshooting, and have replaced the air admittance valve, twice, just in case. The p-trap has been taken off and it is perfectly clean and new. We have snaked the drain under the sink all the way to the tank, as well as snaked the roof vent, with no effect. I used a shop-vac to suck out the gray tank from the bottom to see if there was a clog there, and it worked for about an hour. We have tried to keep the grey tanks closed to see if the sink will continue to drain, no luck. The only solution that keeps the kitchen sink draining is to keep all 3 waste valves open, including the black. This is not an acceptable solution, and I need some ideas about what might be going on.
It sure appears that everything has been checked and then checked again. Certainly an issue that needs to resolved in some manner. It sounds that there is pressure building up in there the plumbing downstream. There needs to be a balance of pressures one would think for there to not create an airlock. That’s why opening the valves helps. It probably isn’t but one wonders if the tank is somehow is not vented properly. Perhaps a snake with a plumbing scope from both ends could give a picture of a problem. This problem sounds like something Heartland would really be interested in since it’s a new rig and others rigs are created equal.
 

JohnDar

Prolifically Gabby Member
Since you've snaked both the drain and the roof vent and found no obstructions, the possibility exists that the roof vent extends too far into the tank, thus not allowing pressure release when water flows into it. Opening the drain valves to get flow sounds like that might be a consideration since that's releasing the pressure. Sound far-fetched? Others have reported similar problems with their toilets and black tanks due to the roof vent dropping down or being installed too long.

How to check? Using a tape measure, extend it down the roof vent pipe and catch the tab on the end of the pipe. Record the length. Then extend it until you hit the bottom of the tank. The difference will be how high the end of the tube is from the bottom of the tank.
 

Chrisandsama

Well-known member
Since you've snaked both the drain and the roof vent and found no obstructions, the possibility exists that the roof vent extends too far into the tank, thus not allowing pressure release when water flows into it. Opening the drain valves to get flow sounds like that might be a consideration since that's releasing the pressure. Sound far-fetched? Others have reported similar problems with their toilets and black tanks due to the roof vent dropping down or being installed too long.

How to check? Using a tape measure, extend it down the roof vent pipe and catch the tab on the end of the pipe. Record the length. Then extend it until you hit the bottom of the tank. The difference will be how high the end of the tube is from the bottom of the tank.

This sounds like your in the right direction, if the stack was down too far into the tank and below the waste level it would not vent properly. Im very curious of the solution to this one.
 
Top