black tank back flow preventer

[TLG]

First trip out last year, our black tank rinse back flow valve was busted. I had winterized it according to the dealers instructions, and figured it was just a bad valve. I installed a new one and it worked all camping season. When I winterized last fall, my wife shined a flashlight on the valve (it's located under the bathroom vanity) to make sure antifreeze went through it. You could also see the antifreeze in the lines going in and out of the valve from the storage area. First trip out last week, the new one busted. It has to be freezing, but I'm 100% positive antifreeze went through it. What am I doing wrong?

[illapah]

Others have had good luck with blowing out the line with air and not winterizing.

[dsprik]

When those valves are installed they sometimes (my case) put a pretty stressful bind on the in and out "U" shape. Mine finally cracked and split. Jarring up and down the road was too much for it. I called Keystone/Montana and they promptly sent me a new one for free. I reinstalled only fastening ONE leg to the wall stud - not both.

[sreigle]

I can't check right now but you might look at where the hose connects to the black flush connector and see if it has a pin in the center. You might have to pry out the washer/screen combination if it has one. If you push that pin it should release the pressure so that valve is not full of water. That pin at the connector is also a backflow preventer.

When we had to winterize we didn't have the backflush so I have not had a problem with it. However, I did have the same problem on the city water fill back in those days. Releasing the pressure was the key.