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Ask Dave: My RV’s kitchen sink holding tank does not drain

Dear Dave,
My RV’s kitchen sink has its own drain tank. I went to dump all my tanks and when I opened the one for the kitchen nothing ran out. I opened and closed the valve a couple times and just a little water came out. I’m scared my valve is closed and will not open. Any suggestions? —Ronald, 2018 Keystone Montana

Dear Ronald,
Are you sure the kitchen sink has its own holding tank? This is very uncommon due to the small amount of water that would be used. I pulled the spec’s from a 2018 brochure. They only list fresh water and gray water capacity total and do not break down how many tanks.

Typically, the kitchen and bathroom sinks are plumbed into the gray water tank along with the shower, but not always. It really depends on the floor plan and the proximity of the sink to the closest tank. Your kitchen sink might go to the black water tank if it is the closest or if there are outriggers from the chassis in the way of the gray water tank. The challenge with fifth wheel and other trailers is the actual tank and/or valve is far away from the handle and bayonet you attach to.

My guess is that you have two separate gray water tanks and remote handles like these with a corrugated underbelly covering and assume one of the tanks is dedicated to the kitchen sink. The average RVer typically uses a minimal amount of water doing dishes in the sink, so having a dedicated holding tank for the one or two gallons used occasionally would be a waste of space. However, as I’ve said many times… I have learned to never say never when it comes to what RV manufacturers will design.

Figuring out where the RV’s kitchen sink drains to

I would dump all the tanks first and make sure the gauges inside showed empty. However, this does not mean they are necessarily empty—as we all know how accurate those can be. But you can see if the gauges show partially full and then empty and get a good idea. Leave all the drain valves open and place a garden hose in the sink drain and let it run at a slow flow. You should see water coming out the drain hose and should be able to identify what valve it is coming from as there should be some flowing sounds. You can also shut off one valve at a time to see if it stops.

If you have no water coming out of the hose, check your fluid level indicator inside to see if one of the tanks is filling up. Keep a close eye on the level gauge and the sink to make sure it doesn’t back up into the sink. That is why you only want a slow flow.

If the valve isn’t opening…

If you do have a dedicated tank for the RV’s kitchen sink drain and it is not dumping when you pull the handle, then it’s most likely the valve is not opening. It could be a broken cable to the valve or even a cable that has gotten stretched and is flexing underneath and not pulling the valve open. We have covered this in a previous post; However, if you have a handle with a cable going to the remote valve, it needs to be secured at 24” from the handle and at various spots to the actual valve. If not, the entire cable assembly moves or flexes and doesn’t have enough force to pull open the spade valve.

Here is the recommended installation from the Valterra service manual:

Cable or valve?

It could be a flexing of the cable or a broken cable to the valve that is preventing it from opening. Now the challenge is finding the valve hidden underneath the corrugated underbelly material. If you can find the valve, rather than removing all the underbelly material, you can cut a small section out with a razor knife to locate the cable and valve. Start with a small square about 6” from the handle as it will start with a hard sleeve from the handle and then transition to the covered cable. Once you locate the sleeve and the cable you should be able to see what direction it goes and cut smaller pieces to find the valve. Here, you can verify if it is the cable or if you need to replace the valve.

Whatever repair needs to be done, once you are finished you can cover the holes cut into the material with a similar corrugated plastic available at most home improvement stores. Look for metal outriggers or solid mounting points in the chassis and cut larger pieces of the material to cover the hole and fasten to those points with self-tapping screws. You will also want to add a little silicone around the edges to seal it tight and you may need to add some insulation.

Dave Solberg is a leading expert in the RV industry and author of the “RV Handbook” as well as the Managing Editor of the RV Repair Club.

Read more from Dave here

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Cecilia
2 months ago

I don’t understand why Dave assumes the kitchen doesn’t have its own tank if the OP has a separate valve handle for it. We have an Arctic Fox fifth wheel and we have three valves — one for kitchen, one for bathroom and one for black tank.

Mike
2 months ago

Dave, my rig, a 5th wheel 2015 Crusader, does actually have a separate grey tank for the kitchen. In our case it is actually the first one to fill on a routine basis. I guess we either eat too much or shower too little!

Bill
2 months ago

I am familiar with such a problem. It is called a “food dam” that builds up at the valve. The incident I am referring to was cleared by blowing compressed air into the drain. It wasn’t pretty and actually very messy as one can imagine.

ronald
2 months ago

ok Dave, you didn’t answer the question completely. How do you get the valve to open if it is stuck and the tank is full?? How could you drain the tank so you could replace the valve?

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