Black tank flush out

[MaxwellD]

Anyone know why alll of a sudden I cant get water to go into the black tank to flush it? Could this be the backflow relief valve I keep hearing about? If so, where is it located? My old unit had a simple spring-loaded one way valve that activated with pressure but this one looks different on my 2018 3730 FL Montana. Ideas? Yes, water is on.

[RoadRunnerTR21]

If you are in Tyler, TX call over to the RV Station and talk to one of their techs.

[scottz]

Originally Posted by MaxwellD

Could this be the backflow relief valve I keep hearing about?

Possible but unlikely. If the anti-siphon valve malfunctions, the usual result is water spraying out of it. The hose connectors come with or without a check valve built in. The fresh water intake should have a check valve (behind filter screen), the black tank flush should not, but I have heard of units with the wrong connector installed. All you have to do is look into the fitting to see if there is a check valve or if it is open. If they mistakenly put a connector/check valve on the black tank flush, it is possible (again, I think unlikely) it is stuck and not opening.

First of all, how do you know it is not flushing? Mine is very quiet.
If it isn't, check the easy things first. 1. Look for malfunctioning check valve at hose connector. 2. Check for kinked line somewhere. 3. Remove anti-siphon device. 4. (Last) Check inside black tank. If a dealer is convenient, let them take care of it under warranty.

Here are photos of a connector with and without a check valve (intake screen removed for photo).

[MaxwellD]

Originally Posted by scottz

Possible but unlikely. If the anti-siphon valve malfunctions, the usual result is water spraying out of it. The hose connectors come with or without a check valve built in. The fresh water intake should have a check valve (behind filter screen), the black tank flush should not, but I have heard of units with the wrong connector installed. All you have to do is look into the fitting to see if there is a check valve or if it is open. If they mistakenly put a connector/check valve on the black tank flush, it is possible (again, I think unlikely) it is stuck and not opening.

First of all, how do you know it is not flushing? Mine is very quiet.
If it isn't, check the easy things first. 1. Look for malfunctioning check valve at hose connector. 2. Check for kinked line somewhere. 3. Remove anti-siphon device. 4. (Last) Check inside black tank. If a dealer is convenient, let them take care of it under warranty.

Here are photos of a connector with and without a check valve (intake screen removed for photo).

Thanks again for the good info.. Today I located and removed the anti siphon ball valve located at the top of the inlet leading from the black tank flush line. It was good up with a muddy substance preventing the ball from breaking vacuum. Cleaned it and re-installed - so far so good. The tank is at least filling so I will be able to flush it as it was designed. This park has really bad water so this probably wont be the last time I have to do this.
Max