water leak under bathroom sink . $70K nightmare

[ChuckS]

Yes look way up high underneath your bathroom sink for two lines... usually PEX and you should see the plastic vacuum breaker valve or anti anti siphon valve. Same thing.

Replace it was a brass unit for years of worry free use or be prepared for water leaks in bathroom

I don’t use my black flush out. I’m lucky my black tank line feed from sewer dump to tank is flat and level.

I use clear coupler with hose connection and waste gate. I can see when tank is clean.

[itat]

Originally Posted by Jacketsbum

Ok I'm the ignorant one here. I hook up a hose to flush my black tank, the water sprays into the tank to rinse out whatever. Sometimes I close the waste valve to fill the tank to gather waste not being hit with the spray. Eventually the waste water coming out clears up and I disconnect everything. What vacuum or siphon am I creating? I'm not quite getting this?

In addition to what chuckster57 posted, that anti-siphon valve, also know as a vacuum breaker valve and backflow preventer valve, is used to prevent any possibility of black tank contents pushing back toward the source potable water supply and therefore contaminating the source water.

Although it would be an unusual, even rare, occurrence, its possible in at least a couple scenarios I can think of:

1) The water main supplying your water springs a big leak and starts to drain causing a vacuum in the hose you're using to spray/fill the black tank. Nasty stuff in your black tank might be sucked out of the tank and back to the source water contaminating the entire system of the campground.

2) You overfill your black tank because you got distracted by a friendly neighbor. The level in the black tank rises above the valve and starts pushing water back against the valve. With the toilet valve sealed, no black water comes out the toilet but the water level rises to the roof through the vent pipe. If the water pressure from the source can't counteract the force ("head") of black water, the black water can push out of your black tank and contaminate the source water system.

As I said, these are rare situations but they've happened often enough that the use of the valve is in plumbing codes.

The worst cases I'm aware of are the one in Michigan that many Americans have heard of, and one in Walkerton, ON. In Walkerton, the source water well for the community got contaminated by surface water overflowing into the well. The well was in a farmers field where cows graze and the surface water was contaminated by cow "manure" which went straight into the well and wasn't treated properly by trained staff before it went into the water distribution system. Seven people died and about 2300 became very ill due to E. coli contamination. Google "Walkerton water tragedy".

Its very serious stuff.

If your valve leaks or breaks and you have to remove it, please be sure to use something equivalent in its place to protect the campground's water system!

[Local150]

Originally Posted by ChuckS

Yes look way up high underneath your bathroom sink for two lines... usually PEX and you should see the plastic vacuum breaker valve or anti anti siphon valve. Same thing.

Replace it was a brass unit for years of worry free use or be prepared for water leaks in bathroom

I don’t use my black flush out. I’m lucky my black tank line feed from sewer dump to tank is flat and level.

I use clear coupler with hose connection and waste gate. I can see when tank is clean.

Thanks,, looked under sink today but didn't see anything ,, will look up further 2 morrow, just glanced in there, saw a white and a red water line, like I said will look up further by the top of sink. I also have a clear elbow in the sewer line ,, my lights have always indicated levels correctly, just thought I would clean it,, doubtful will do it again,, thanks for your input

[Local150]

Originally Posted by Local150

Thanks,, looked under sink today but didn't see anything ,, will look up further 2 morrow, just glanced in there, saw a white and a red water line, like I said will look up further by the top of sink. I also have a clear elbow in the sewer line ,, my lights have always indicated levels correctly, just thought I would clean it,, doubtful will do it again,, thanks for your input

My next step

[rdhouston]

Ok so I ditched the valve under the sink in favor of a backflow preventer on the end of my blackwater tank flush hose. We'll see how it goes later, too cold to de-winterize just yet.

[Jeremy888]

rdhouston , good job. exact same fix that I used . Have not had a problem since .

[srvnt]

Bypass it and use a check valve on the hose

[Bostongone]

Probably not a good idea to remove the back flow preventer and replace with straight thru regular connections and figure on just using a back flow device on the end of your backwash hose. You may remember to use the correct hose religiously but what about the next owner especially if unit is traded and nobody knows about the mod?

[slow]

Leave the back flow connector on the inlet to the trailer.

[German Shepherd Guy]

So the clean-out inlet for my black tank is located on the back of the trailer. It is a standard hose fitting that I attach a garden hose to. I then flush out the black tank. The back flow preventer talked about being left on the line. It has a garden hose fitting? Or are there additional fittings needed to purchase to make that hook up? I like the idea of just eliminating the plastic piece under my sink, but living 65 miles from the nearest hardware store need to use amazon to purchase the back flow device and still am not quite certain what parts I need. The ones I see on amazon are called Mueller/B & K 108-904RP Backflow Preventer-Vacuum Breaker.

Made of brass, looks like a hose connection, and is dirt cheap. Can this really be the fix to a future leak problem?




Sorry for being dense about this, thanks in advance


Oak

[66joej]

Yes that does the same job as the one under the sink.
That bolt is for a permanent installation as the head breaks off when tightened on the hose.