221RB Black tank flush clogged?

[Cleandave]

Hi all. I just bought my 2020 221RB from a coworker a few months ago. I've been living in it full time for fire season and haven't had any issues with it until now. When I hook up a hose to the black tank flush port and go to flush, nothing happens. It just leaks from the connection and makes makes funny pressurizing noises. Nothing coming out in the tank or from the tank drain. I removed the the connection port from the aft exterior wall but can't see there the line goes, even with a small inspection mirror. I've done some searching around the forum and keep seeing "vacuum valve" pop up in black tank issues. Could this be my problem? I don't even know what this vale does or where it is though.

[Ynot4me2]

Have you verified the screen where the hose connects for debris that could be clogging? If you have access to an air compressor, maybe try flushing at 40psi maybe 50. I'm not to familiar with your rig but that vacuum valve will be inside, close by to your flush port. On ours it's under the bathroom sink. Yours could be behind the shower wall. Hopefully another member with the same rig will chime in soon.

[Soundsailor]

Hi all. I just bought my 2020 221RB from a coworker a few months ago. I've been living in it full time for fire season and haven't had any issues with it until now. When I hook up a hose to the black tank flush port and go to flush, nothing happens. It just leaks from the connection and makes makes funny pressurizing noises. Nothing coming out in the tank or from the tank drain. I removed the the connection port from the aft exterior wall but can't see there the line goes, even with a small inspection mirror. I've done some searching around the forum and keep seeing "vacuum valve" pop up in black tank issues. Could this be my problem? I don't even know what this vale does or where it is though.

First off @Cleandave, welcome to the forum and the Grand Design family. You're on the right track asking for help here, many experienced owners who can help. I don't have the same coach as you, but I'm sure someone will be able to give you some insight on how to solve your issue.

[Cleandave]

Have you verified the screen where the hose connects for debris that could be clogging? If you have access to an air compressor, maybe try flushing at 40psi maybe 50. I'm not to familiar with your rig but that vacuum valve will be inside, close by to your flush port. On ours it's under the bathroom sink. Yours could be behind the shower wall. Hopefully another member with the same rig will chime in soon.

I have checked the screen. There are no visible blockages that I can see anywhere. Can anyone tell me how to test the vacuum valve?

[FT4NOW]

It sounds more like a pinched line, similar to folding a garden hose to stop water flow.
The tank flush line is made from a flexible material, it isnt a hard line. Depending on your rig will determine where the vacuum breaker is located.

I'd disconnect the vacuum breaker and run water through the flush line to collect in a bucket and see if that portion of the system is blocked.

Another option is to remove the vacuum breaker and do a bench test on it out of the camper, if both of those are good, you would have to drop the underbelly and see if the line is pinched or not and go from there.

[Cleandave]

It sounds more like a pinched line, similar to folding a garden hose to stop water flow.
The tank flush line is made from a flexible material, it isnt a hard line. Depending on your rig will determine where the vacuum breaker is located.

I'd disconnect the vacuum breaker and run water through the flush line to collect in a bucket and see if that portion of the system is blocked.

Another option is to remove the vacuum breaker and do a bench test on it out of the camper, if both of those are good, you would have to drop the underbelly and see if the line is pinched or not and go from there.

So I found the breaker and pulled it out. Seems to not be working properly. Ordered one for $10 on Amazon so we'll see if that fixes it in a couple days.