2004 HR Endeavor Black Tank Flush Leak

[Phil8920]

Good afternoon everyone. Having a major issue here, cannot figure it out. After I dumped my black tank, I hooked up water to my black tank flush. I was at a dump station with no hose connection, so I hooked up my flush hose to my outside water spigot, ran directly to the black tank flush inlet, and turned the pump on. After about 30-45 seconds of water running, nothing was coming out the drain. Yes, the drain was open and I have a clear elbow for visualization. Went inside to inspect, had major water coming from under my vanity sink. I have the 40PDQ, the vanity by the shower is where it was leaking.

I assumed the flush line went directly to the black water tank. Does anyone know where to find the plumbing diagram for a 2004 HR Endeavor 40PDQ? I've used the blank tank flush numerous times and have never had this issue.

Thank you in advance for any insight or advice.

-Phil

[vseasport]

Welcome to the forum!
My guess is you have a plumbing leak under your vanity that is not related to the black water flush. Dis-connect your flush hose from the spigot and turn it off. Bet you will still have the leak.

[96 Wideglide]

You didn't have enough pressure to close the vacuum breaker, so the water leaked out there, into the vanity.

They need something like 45psi to close.

[96 Wideglide]

Originally Posted by Phil8920

I assumed the flush line went directly to the black water tank.

-Phil

No, your black tank flush goes into the vanity, up to the vacuum breaker (which will be close to vanity sink height), then down back thru the floor, to the black tank cleaning nozzel.

This is to ensure nothing from the tank can contaminate the water supply.

[windsorbill]

As Ben says, up under the bathroom sink.
Here's what they look like.

https://www.lowes.com/pd/Cash-Acme-B...ker/1002859010

I've seen them in plastic too, but those are cheap and are prone to fail.

[Phil8920]

Originally Posted by windsorbill

As Ben says, up under the bathroom sink.
Here's what they look like.

https://www.lowes.com/pd/Cash-Acme-B...ker/1002859010

I've seen them in plastic too, but those are cheap and are prone to fail.

Thank you guys! After some testing, it was in fact leaking from the anti-siphon valve. But, here's what I learned.

With the flush line disconnected and I turn on the pump, it cycles until pressurized...no leaks. When I hook up city water to the RV...no leaks even when flushing the tank. So I'm assuming that when using the water pump directly to the flush line, it had plenty of flow but no pressure to close the anti-siphon valve. Lesson learned!!

BTW, this was my first post here. I've read countless threads over the past 2 years though. I've been a RV owner since 1992, this is my first MH though. As my wife and I were researching motorhomes, I would go to this forum for insight on a particular brand/model. We looked at countless motorhomes, and kept coming back to the Holiday Rambler or Monoco Coach ones as our favorites. One of the deciding factors, this Monoco Owners forum! Every person I talked to when looking at MH's pointed me to this forum for answers. We've had our new-to-us HR Endeavor since February, have put over 5000 miles on it already, and I have turned to this forum a number of times for ideas and solutions. Again, thank you.

Hopefully...in a couple more years of hard work, the wife and I will be retiring and enjoying our MH 24/7/365!

[96 Wideglide]

Phil, even when you are using city water to flush your tank, open the spigot quickly, so that surge of water will seat the vacuum breaker !