Black Tank Flush Not Working

[rgolding]

After extended "boondocking" we had a very full black tank. Got to a campground with full hook up and emptied. All seemed fine. Hooked up black tank flush hose to give a good rinse and nothing. Cannot hear any water rushing in as it has in the past.

Decided we may have been so full that we clogged the jets at the end of the black tank flush.

Put in 15 gallons of water and some ice cubes down the toilet and drove the final 200 miles back to our home base. Tried to dump again and hooked up black water flush. Still not hearing the normal rinsing sound and water does not seem to be raising in tank, so feel there is still blockage, somehow.

Any ideas? Maybe compressed air? Plastic safe Liquid plumber or Drano in the black tank flush line. Looking for ideas. Any help or opinions is truly appreciated.

[norty1]

I believe I would try air pressure first.

[staineous]

Get yourself some TankTech and use it regularly. With this stuff you don't completely empty your tank and it works extremely well. We have been running this for several months in our 37TS and our tank is performing perfectly.

To fix your problem you would put a couple ounces of this stuff in your tank and let is stay in the tank while the RV is stored. If you are currently using the camper just keep using it and follow the TankTech instructions. I used to be a fanatic about flushing my tank every time I dumped until I found this stuff. Now that I follow the instructions we never have odors and the sensors work perfectly and we are not using the horrible blue stuff any more.

Here is a link to their web site.

I buy it off Amazon.

This will correct your problem and alleviate future problems.

[norty1]

My black tank is never empty. After dumping it, I always put 3-4 gallons of water back in it.

[repeach]

I had the same issue on my 2006 Seneca. Turned out it was the air gap check valve was stuck closed. I tried air pressure and it did not help.
I ended up replacing the check valve. On both the 2006 and 2018, the check valve is located under the bathroom sink. They run from the water inlet under the floor to where the water lines go up to the sink. The check valve is at the highest point.
Just google "black tank check valve" and you will see pictures and be able to purchase a new one. They are pretty cheap.

[staineous]

Originally Posted by norty1

My black tank is never empty. After dumping it, I always put 3-4 gallons of water back in it.

With this stuff, you will leave a few gallons in the tank when you dump. As in, close the valve before the tank is completely empty. This maintains the bacteria culture in the tank to do their thing cleaning on the tank all the time. They say you will only use the tank flush once a year or so. This is completely counterintuitive to the way I have always maintained my black tank, but it is working very well so far.

The material on their web site is a good read and I thought I would give it a try.

[EA37TS]

More than likely the vacuum breaker is the culprit.

https://www.amazon.com/Vacuum-Breake...s%2C172&sr=8-5

Should be under the bathroom sink.

[rgolding]

Thank you guys, didn't think of that being the problem. Found it under the bathroom sink and sounds easier to replace than any of my other ideas. Ordered and will report back results after install.

[rkresge]

Originally Posted by rgolding

Thank you guys, didn't think of that being the problem. Found it under the bathroom sink and sounds easier to replace than any of my other ideas. Ordered and will report back results after install.

I vote for the vacuum breaker check valve; they're notorious for going bad. I just replaced mine a couple of weeks ago, easy to do. Although you may need to be a contortionist to get to it.

Good luck!

Roger

[repeach]

Originally Posted by rgolding

Thank you guys, didn't think of that being the problem. Found it under the bathroom sink and sounds easier to replace than any of my other ideas. Ordered and will report back results after install.

did you get your check valve replaced? was that the issue?

[rgolding]

We have been home since a couple of days after Memorial Day and the Seneca has been in storage at our Son's place. We load and begin traveling today. I have the new anti-syphon unit and plan to install it over during this next 10 weeks in the Seneca. I'll update this forum upon installation, reporting if that solved the problem. Thank you for the interest.

[rgolding]

Back to report on the anti-syphon valve replacement. I did replace the old with the new and there was no change. Units are identical, except the replacement has a white nylon ring retainer holding the spring in place internally in the pipe.
I am able to make the old one open and close, the new one has more pressure against it and cannot be worked as easily.

So next step is to apply a little air into the system. I'll do this from under the sink where this anti-syphon valve is installed. Should be able to rig up a simple screw on adaptor where the anti-syphon valve screws on.

If interested, stay tuned. The adventure continues. Please understand this is not a priority in my life, so we work on it when the initiative strikes.

[repeach]

thanks for the update.
I thought it would have been the check valve.
Now I am really curious what it turns out to be.

[mprosser]

I had same issue... turns out the black tank flush nozzle was clogged up. Replaced it and now it works.