Gray tank not draining

[Old Bear]

This is a hard one. 2014 Rushmore Lincoln. I have figured out that the bottom gray tank drain handle matches with gray tank #2, but I do not know if that is shower/bathroom sink (I'm guessing they drain together) or the kitchen sink. Anyway, I pull the handle to drain, the handle pulls out like it seems it should (similar to the other two), but hardly any water drains out. I will have to leave it open for a few days to get it empty.
I have glanced at the bottom of the RV, that is some serious sealing. It looks and feels like a thick plastic board, solid, and mounted on either side by a long aluminum strip and screws. Even where the drain tubes come through, they are sealed with some type of black firm sealant. I do know that I can get into the crawl space where the backside of the drain cables are (along with water filter, water heater, furnace and such) but I haven't done so yet.
What I don't know: perhaps the cable needs a major adjustment? is there an access panel on top to get to the valves? if this is the kitchen sink drain, did the previous owner dump hot grease down the drain and it solidified at the valve? I am really at a lose on what to even try! Suggestions?

[Dayle1]

Do you have an outside kitchen? If so, that tank may be only for the outside sink and if you rarely use it, the tank will be empty. So everything may be ok.

The other possibility is that when holes were drilled thru the tank to install the fill and drain lines, the cutout dropped into the tank and is now stuck in the drain line and blocking flow.

[woodwalker]

Leave both grey levers open until you know the tanks have emptied. Close them and then turn the water on to the kitchen sink for 10 min. Open the valve to see which one the water comes out of. Once empty close again and do the same to bathroom sink then shower etc. You will then know what drain goes where

[Old Bear]

Originally Posted by Dayle1

Do you have an outside kitchen? If so, that tank may be only for the outside sink and if you rarely use it, the tank will be empty. So everything may be ok.

No outside kitchen.

Originally Posted by Dayle1

The other possibility is that when holes were drilled thru the tank to install the fill and drain lines, the cutout dropped into the tank and is now stuck in the drain line and blocking flow.

Well, that would be bad. It looks like getting to those tanks would be a HUGE job.

[Dayle1]

Originally Posted by Old Bear

Well, that would be bad. It looks like getting to those tanks would be a HUGE job.

I would try sliding a garden hose up the drain line as far as possible, smallest diameter with hose end cut off. Then turn the water on and see if you can clear the problem. May not work or the obstruction may return in weeks or months, but worth a try.

[2slick]

I don't believe the cable valves are adjustable. I cut access in the bottom (coroplast) of ours to change our black tank valve to electric. You can seal it back with gorilla tape.


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[Old Bear]

Originally Posted by 2slick

I don't believe the cable valves are adjustable. I cut access in the bottom (coroplast) of ours to change our black tank valve to electric. You can seal it back with gorilla tape.

I assumed that there would be a bunch of insulation that I would have to deal with as well? Not the case? How did you identify where the valves were at, or did you cut a pretty good section.

I wondered about changing over to electric as well. Perhaps a future job!

[2slick]

Originally Posted by Old Bear

I assumed that there would be a bunch of insulation that I would have to deal with as well? Not the case? How did you identify where the valves were at, or did you cut a pretty good section.

I wondered about changing over to electric as well. Perhaps a future job!

Our 2012 only has the foil bubble insulation in it. I cut it too. Probably a 18 X 24 opening. Just clean the coroplast good before taping. I use acetone.

You might get one of the clear flush fittings and cap it off. Then open only the affected valve, hook up a water hose and see if you can force water back through it. I wouldn't put too much pressure on it though. Could be blockage like someone said previously. Good luck.


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[dedmiston]

I've seen many posts over the years where owners had to drop their tanks to find the obstruction and they found a round cutout disk left over from the initial build where the factory was too careless to catch it or too lazy to fish it back out. "Not my job".

[Dayle1]

Originally Posted by Old Bear

How did you identify where the valves were at, or did you cut a pretty good section.
!

Normally, the tank bottom is not flat, but has a very slight slope with the drain line at the low end. Also the actual valve will be as close to the tank end of the line rather than near the outlet or randomly along the pipe. Finally the direction of the pipe as it exits the underbelly should point you in the right direction.