Black tank flush

[Freebirds]

Our black tank flush does not work. The dealer has changed the back flow valve which did not help. The dealer feels it must be stopped up inside the tank which is going to mean cutting the underbelly (Trilogy has a solid underbelly - not in pieces) and removing the gray tank to get to the black tank above it. I don't know if I want the dealer to do that extensive work on it.

Has anyone else had a stopped up black tank flush and what was done to correct the problem?

[CC38EL]

We have not had the black tank flush stop up but I wouldn't know it if we did since we have never used one in our years of RVing. Not that we don't want to, it's that we've never needed to. We clean the tanks in a different way.

But I wanted to let you know that we just had our black tank valves replaced and the dealer wanted 4 hours to drop and then reattach the bottom cover.

At $125/hour, that's pretty steep.

I can't imagine what the total cost would be if you include dropping tanks.

[KenHwy61]

Without knowing your physical or mechanical ability you will have to decide what you feel comfortable doing. If the black flush was working and stopped it may be plugged inside the tank and either soaking from the inside or leaving the flush line hooked up and pressurized may eventually soften and clear the obstruction. Just be sure to leave the drain valve open. If the black flush has never worked the tubing to it may be kinked. If it were me, I would not hesitate to open the underbelly and look for myself. Most RV repair is well with in the abilities of most handymen. Parts are very easy to get online or at a home improvement store. Empty tanks are not heavy. I just removed my entire underbelly cover and removed my fresh water tank. I also just removed the black water drain valve and cleaned some blockage. Laying on your back under a trailer isn't overly fun but going to the dealer and paying top dollar for often sub-standard work is worse.

[BamaBob]

I take it by your post that it did work at some point in the past?

What happens when you connect the water to the black tank flush inlet, open the black tank and turn the water on? do you get any flow at all?

[Freebirds]

Originally Posted by BamaBob

I take it by your post that it did work at some point in the past?

What happens when you connect the water to the black tank flush inlet, open the black tank and turn the water on? do you get any flow at all?

There is no flow at all.

The work will be done under a service contract. However, that is such extensive work. The Trilogy is made differently from most RVs in that the gray water tank is immediately below the black water tank. The gray water tank has to be totally removed to get to the black tank. Also unlike other trailers, the underbelly is one solid piece so the dealer will have to but an opening and then patch it back in. Will it ever be back like original?

My DH does no trailer work at all. We are hoping to find a solution that will work without going into the tank. We bought the piece for the drain that will allow us to fill it to the top through a hose from the drain hole. Of course no way to fill it through the toilet.

[Freebirds]

And yes, the black tank flush worked for over a year.

[youroo]

Free bird all of the Rockwood and Flagstaff units with (Enclosed Underbelly) have Front to Back (1) piece coverage! So your unit is Not Special! Youroo!!

[Freebirds]

Originally Posted by youroo

Free bird all of the Rockwood and Flagstaff units with (Enclosed Underbelly) have Front to Back (1) piece coverage! So your unit is Not Special! Youroo!!

Irrevelant...ha ha It's the only one we've ever owned like that - I didn't mean it was the only one!!

The important thing is what can we do about a stopped up flush. I'm thinking of filling the whole tank up with ACID.

[jeff64]

I think if I could access a spot on the line downstream of the backflow preventer, I'd pull the hose clamp and duct tape a shop vac to it and alternately reverse the flow and see if I couldn't get lucky and get it to move first, before, I resorted to more invasive or extreme proceedures. Jus' a thought!

[John Hagen]

I think I would try the following if it were me:

1. At the hose connection for the black tank flush in the basement... Disconnect the hose connection from the black tank flush hose. Apply compressed air to the line heading to the black tank and see if you can get air to flow. May have to use 60psi or so. Make a tight seal where you inject the air.

2. If no luck trying the above... Go to where the check valve is installed. Disconnect the check valve and with check valve removed, try blowing air in from the basement connection as per instructions above to see if it comes out where you disconnected the check valve. If air flows, you know line is good to that point.

3. Apply air pressure to the hose/tube that continues to the black tank from the check valve. Do not have check valve installed during this test. If air flows, your new check valve is bad or was installed backwards. Doesn't matter if check valve is new; it could be defective or was installed backwards.

4. You can manually check the check valve in the same manner. Blow air in one side - should flow. Blow air in from other direction - should not flow. This would tell you if it was installed correctly and if it is operating correctly.

5. If the above tests fail, time to drop the belly panel...

John

[Freebirds]

John Hagen: We have tried using the air in the basement but not where the check valve is. The dealer replaced the check valve but I hear what you are saying. If I can get to the check valve, I will try your suggestions. If not, I will ask the dealer to do that before they do more invasive work.

Jeff: I'm not sure if we would be able to access that point but I appreciate the suggestion.

[Cypressloser]

We had a similar issue and our Trilogy is probably plumbed the same as your's. When you remove the cover over the water manifold and look behind it (use a flashlight) you can see where the black tank flush connector is hooked up to a white, braided 1/2" hose. This hose developed a kink over time and cut off the water flow, the fix is to disconnect the hose and install a 90 deg. elbow - 10 min. tops.
Take a pic. with your cellphone and take it to the hardware store and ask an employee to help you find the correct fitting if you're unfamiliar with plumbing.

[kwoodrg]

Our rear black tank flush did not work when our unit was new. The check valve was indeed installed backward. So, if the mfg will install a check valve backward then you can be sure the hacks at a dealership can install it backward. absolutely check that first. it requires almost no effort. the valve will be marked with an embossed arrow indicating the direction water should flow. if the arrow is backward then no water will ever reach the tank. Good luck!


2014 Dynamax Trilogy 37BH
2015 Ram 3500 DRW

[Freebirds]

Originally Posted by Cypressloser

We had a similar issue and our Trilogy is probably plumbed the same as your's. When you remove the cover over the water manifold and look behind it (use a flashlight) you can see where the black tank flush connector is hooked up to a white, braided 1/2" hose. This hose developed a kink over time and cut off the water flow, the fix is to disconnect the hose and install a 90 deg. elbow - 10 min. tops.
Take a pic. with your cellphone and take it to the hardware store and ask an employee to help you find the correct fitting if you're unfamiliar with plumbing.

I left out that the dealer did that the first time we took it in to be repaired. They sent us home saying it was fixed. That wasn't it. The dealer has worked on it three times and we are still going to have to return for the fourth trip.

[Freebirds]

Originally Posted by kwoodrg

Our rear black tank flush did not work when our unit was new. The check valve was indeed installed backward. So, if the mfg will install a check valve backward then you can be sure the hacks at a dealership can install it backward. absolutely check that first. it requires almost no effort. the valve will be marked with an embossed arrow indicating the direction water should flow. if the arrow is backward then no water will ever reach the tank. Good luck!


2014 Dynamax Trilogy 37BH
2015 Ram 3500 DRW

I wish we could figure out where the check valve is and we would try to do it ourselves. We definitely want them to try a new check valve before they tear everything out. Forest River could have made the flush easier to get to. Our dealer says it has a hose that snakes here and there!!

[kwoodrg]

My check valves are under the front and rear bathroom sinks


2014 Dynamax Trilogy 37BH
2015 Ram 3500 DRW