Back Pressure-Black Tank Flush

[Lynn1130]

There are many threads about related issues but I am still unclear about how to check to see if any of those are the answer to my problem.

The problem:I recently dumped and was trying to flush the black tank. It appeared that no water was going into the tank from the water connection and there was back pressure on the water hose. It was below freezing and I though that the brass valve behind the wall was frozen so I waited until I got to the storage facility at home to complete the flush. This time it appeared that I was getting water through to the black tank but at a slow rate and that there was still back pressure on the water hose line. Normally I can hear the "rushing" of the water into the black tank. I was not hearing this at the volume that is normal.

The question: What is the brass fixture behind the UDC wall on the flush line and could this be the problem? If not how do I check to see if there is a real problem. And if I find one what is the repair?

 

[porthole]

Your "back pressure" may just be "head pressure"

The back flush line goes from the UDC out through and behind the basement wall, about halfway, turns towards the rear and just forward of the entertainment area it goes up. The square access cover in the bathroom is there to get to the vacuum break that is in the line, and it should be above that hole.

From that brake, back down and forward to the black tank.

So the water you get spitting back is what is in the line up to the vacuum brake.

 

[Lynn1130]

OK, so are you saying to replace that brake? Is it Pexed inline? I have seen other suggestions of what to use here but do you have a suggestion?

Thanks

 

[porthole]

No, what I am saying the water you get when you disconnect the hose, and it comes out of the flush fitting is water in the lines up to that valve. You have a 1/2" line that is probably 12' in length to that valve, filled with water.

I'm not sure what brass valve you have for the flush line. Have a picture?

That break may or not be pexed and is inline.

Could look like this.
//heartlandowners.org/mediawiki/index.php?title=Black_Tank_Flusher

The breakers can fail, but most of the time they fail and leak, not block upped

 

[JohnDar]

If there is a real check valve on the UDC port, it may be stuck, thus restricting the flow (they can go bad). See if there is a short spring loaded tab in the center of it and try pressing it in to see if if functions easily. The OEM plastic fitting in mine broke a couple of years ago and I replaced it with a brass city water fitting, with a check valve in it.

 

[Lynn1130]

I have to make a trip to the storage in the next few days. I will see about a photo.