Black Water Flush

[harris155]

We are the proud owners of a new to us 2009 Monaco Monarch 33SFS.
We got away for the first week and it performed flawlessly except for the black water flush. Cannot get any water flowing in the black tank flush. The check valve on the panel passes water but not the plumbing. I now have some plumbing cleaner in the lines with 50 PSI of air on it but it will not budge. Our old MoHo you could follow all the plumbing under the coach but this one seems to be sealed up rather well. Any ideas where or in which cabinet to start looking for the flush inlet?

[run2]

Not to hijack this thread. I also have this same problem on my 02 Exec. My flush line is concealed rather well also. It never has worked since I purchased my coach used. I also tried air, different types of cleaners, but nothing worked. Up till now I just lived with it but also am hoping someone has an explanation or a fix.

[ArmyEOD]

We have a 06 Diplomat and I had the same issue when it was new. It turned out to be the check valve that is located between the outside flush hose conector and the spray head in the tank. On my coach they access the black tank on the passenger side by removing a couple of screws on the bottom of the coach and then the panel just swung up (I had them install a latch on the bottom so I can access the tank anytime in about 30 seconds). Anyway there is a hose that goes into the tank. They replaced the check valve and all has been good for five years. Hope this helps

[rlbow43]

Happened across this post a couple of days ago, after my flush quit working. I had already called Monaco tech support, and they assured me there was some kind of "check valve" in the coach (2002 Monaco Windsor we bought used not quite 2 years ago) that was higher than the P-trap in the bathroom. Initially I couldn't find anything except the vacuum breakers for the gray water system. Eventually found the "check valve" - behind the washer/dryer - and it was higher than any P-trap in the coach.

So I started checking out the water flow through the flush lines. First I took the check valve out and hooked a hose to the inlet side of the valve. Turned on the water, it came out the other end of the hose. Next, installed the valve in the inlet line and hooked the hose to the outlet side. Water ran out the hose. Problem had to be in the water line from the valve to the flush nozzle, or in the nozzle itself.

Took the water line off the nozzle (just like George said, it was very accessible, just inside the door that is screwed down that covers all the holding tanks - fresh water, black and gray). Immediately saw some brown sediment (poo or whatever...) that seemed to be filling the nozzle. Took a while, but I got all the sediment out of the nozzle. Could see the holes in the nozzle end. Hooked it up. No water out the nozzle - you can easily hear it when it's working.

Had to be the water line. So I got my air hose out, fired up the compressor and blew out the line. Went outside, and there was a final "plug" of brown sediment laying on the ground. Apparently it had been in the water line and the water pressure could not force it around the 90 degree brass fitting, but the air compressor could.

Hooked it up, and voila! Everything works fine. In fact, I think the water flow through the nozzle is better than ever. Not really sure about that, but seems that way.

Now how could this happen? Last week my brother drove the coach while his wife, my wife and I rode our bikes across Kansas - along with about 900 other poor souls. He did all the set-up and tear-down every day. Had never driven a motor home before, but he did a great job - except for the black tank flush. Either I didn't explain the importance of the flush, or he didn't understand the importance. Anyway, the flush was not used when the tank was dumped. It was a hot week, and my guess is the sediment filled the nozzle and back into the water line a bit. When the flush didn't get used, the sediment dried out and created a "soft" solid in the nozzle and water line. After thinking about it, I think the sediment in the nozzle would have been blown out into the black tank by the water pressure, but the plug in the water line was solid enough it couldn't make it around that 90 degree corner in the brass fitting.

I hope my experience will help someone else when problems with the black tank flush happen to them.

I learned:
1. Use the flush EVERY time you dump the black - not sure I haven't but I will never forget this week.
2. If you have to, the flush nozzle is not hard to find & clean on this particular coach.

This week proved the old adage once again, "If you have an RV you better be handy, because you'll be fixing something all the time". Good thing I like to do stuff like this, or I'd be broke and/or crazy by now. Ain't RVing fun!

[Diplomat Don]

harris155....rlbow43 found the problem, but it will happen again. Everytime the black tank got about 2/3rds full, the flush would plug. I believe that when the tank gets full, sludge/paper pushes up through the spray nozzle. Once there, it dries and plugs the nozzle. After this happened a couple of times, I took a 1/8" drill and drilled several holes into the sprayer. Since the sprayer is at the end of the tank, I wasn't worried about spraying, but delivering a large quantity of water. Mine hasn't plugged since.