Black tank and back flow check valve

[24DegreesN]

I have a 2000 Monaco Diplomat. Recently the back flow valve (located under the bathroom sink) started leaking. I replaced it and everything seemed fine. I usually have to dump the black tank every couple of weeks as I'm a full-timer. I just flushed last weekend, and last night it seemed like the black tank was full again. (curious, as it's just me and I could not have possibly filled the black tank in 4 days...) So I got up this morning and flushed...the black tank WAS completely full.

My question is: are there more than "one-way" back flow valves? I ordered the replacement (brass) from Amazon, and it looked exactly the same as the one I replaced (although it was plastic).

I can't think of any other reason there would be so much water in the black tank...I do have a sani-flush, but the water was turned off when I checked it this morning.

[gerdutch]

Question, do you have a black tank flush sytem?

[gerdutch]

Sink drains jnto Grey , and grey tank can fill in 4 days assuming you shower daily.

[Old-Biscuit]

Originally Posted by 24DegreesN

I have a 2000 Monaco Diplomat. Recently the back flow valve (located under the bathroom sink) started leaking. I replaced it and everything seemed fine. I usually have to dump the black tank every couple of weeks as I'm a full-timer. I just flushed last weekend, and last night it seemed like the black tank was full again. (curious, as it's just me and I could not have possibly filled the black tank in 4 days...) So I got up this morning and flushed...the black tank WAS completely full.

My question is: are there more than "one-way" back flow valves? I ordered the replacement (brass) from Amazon, and it looked exactly the same as the one I replaced (although it was plastic).

I can't think of any other reason there would be so much water in the black tank...I do have a sani-flush, but the water was turned off when I checked it this morning.

Water only flows one direction on those 'anti-siphon back flow vacuum breaker' devices.
So if installed backwards no water would flow to black tank via flush nozzle

Do you keep garden hose connected to flush system all the time or only connect when you do a flush?

If all the time......it was not completely turned off or somebody messed with you and turned it on.

If not connected them --------either toilet leaked down/ran continuously, bathroom faucet leaked (if it goes to black tank) OR you didn't really fully dump tank last time


Water from some source had to fill tank........not many possibilities so should be easy to ID where it came from.

[24DegreesN]

The motorhome has a "built-in" system to spray water into the black tank. I "rinsed" the black tank about 3 times with this system when I was flushing last weekend, so I know it worked. (and you can hear it running if you're in the rig, so I would have heard it over the last 4 days...) The toilet hasn't been running/isn't leaking. No garden hose is attached to anything. It's a conundrum, for sure...

[Bob_C]

When mine started leaking, I replaced it with one that has 2 flow gates inside made for a house.....was able to do away with factory plastic one and about 12' of hose