Check valve

[kid]

Had a leak under the bathroom sink cabinet. Appears to occur during the black tank flush procedure. Water escaping from a brass valve under the cabinet and high to the top right. Originally had the flush hose connected to out valve of filter, changed hose to direct line from city hose connection and problem stopped. Any help on this problem....

[kid]

Had a leak under the bathroom sink cabinet. Appears to occur during the black tank flush procedure. Water escaping from a brass valve under the cabinet and high to the top right. Originally had the flush hose connected to out valve of filter, changed hose to direct line from city hose connection and problem stopped. Any help on this problem....

[LK23]

I believe that is the check valve for your black tank flushing. I don't know what coach you have, but my Horizon has the black tank check valve high up under the kitchen sink. I have a separate water hose connection in my water compartment for the black tank flush. If yours is similar, I would suggest you connect and flush while someone watches this check valve for leaks.

[Rocky Larson]

My manual says to be sure to have the dump valve open when flushing. I didn't remember reading that the first time and I had a similiar problem. Hasn't happened since I changed to recommended procedure. I think it has to with building up pressure in the tank.
Now if I want to fill up the tank I wait until its flushed a few minutes,use a hold open device on the toilet then close the dump valve.
Not as smelly as you might think and gives a good flow for final flush out the dump valve. Just don't get distracted and walk away.

[kid]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by LK23:
I believe that is the check valve for your black tank flushing. I don't know what coach you have, but my Horizon has the black tank check valve high up under the kitchen sink. I have a separate water hose connection in my water compartment for the black tank flush. If yours is similar, I would suggest you connect and flush while someone watches this check valve for leaks. </div></BLOCKQUOTE>


Thanks for the info., appears to be the valve you mentioned. Problem solved...Merry Christmas

[Don-Savannah, GA]

I believe the "check valve" under the sink that you are referring to is actually a vacuum breaker, the purpose of which is to allow air to enter the tank when draining it so it will not suck the water out of the sink traps. Generally speaking the vanity sink dumps into the black water tank. The vacuum breaker is actually a check valve, but the flow is in the opposite direction, therefore when you flush the black tank it could be letting wet air out of the vacuum breaker. Theoretically when you force water into the black water tank the excess air should be escaping out of the roof vent not the vacuum breaker.
I have no idea why changing the source of water of your flush hose would affect your situation.

[hamguy]

Interesting information. My '02 Itasca 35U Suncruiser has a vacuum breaker under the kitchen sink for the gray tank and another under the bathroom sing for the same tank. They put the vacuum breakers in to keep from sucking water from the pee-traps when dumping. My black tank has NO check valve as it is vented directly and has no pee-traps in the plumbing.

I have never heard of a system where one cannot flush the toilet without the dump valve being open. That goes directly against commonly accepted practice and would eventually lead to a black mountain in the tank. Strange.