View Full Version : Black tank flush issue

05-11-2011, 10:56 AM
The other day I was finally able to hook up a hose to the black tank flush connector. When I turned the water on it caused the pressure relief valve to go off on the water heater. Any ideas why this happened? Did I miss a step?

05-11-2011, 11:26 AM
Something does not sound right about that. I don't know that much about how trailers are built, but I don't think there is suppossed to be any way that black water could enter the fresh water systems. Are you sure that was the black water connection? I will be very interested to other replies.

05-11-2011, 12:24 PM
Must have been on the wrong connection. Black water flush is just a short hose that goes to the spray nozzle inside the black tank. Nothing else connected to it...Don

05-11-2011, 01:08 PM
Did you disconnect the fresh water or shut it off so you could flush your tank ?If there was only some
or no water in your water heater and it was heating maybe the relief valve would go off.Never turn
off the water when heater is on.

05-11-2011, 03:07 PM
I did shut the water off. I hope that was what it was. It is still working and if that caused it, I am lucky. I did look into the system a little more and there is no more to it. Just open the gate and turn water on. I am not sure what would have caused it.

05-11-2011, 05:19 PM
Well some of this sounds fishy, first the black tank flush system is a closed system with no connections to any other part of the trailer. The line goes from the UDC up the wall to a back flush preventer that is located above any other part of the water system and then to the tank. As far as I can see you must have hooked to the fresh water inlet. If you had to turn a lever you must have turned a by-pass valve, It will be interesting to hear what really happened.

05-11-2011, 05:38 PM
No other valve but the one that turns the water on to the hose. I oft the original white hose hooked to the fresh water inlet and hooked another hose to the connection below it. Marked black tank flush.

Chuck Richard
05-11-2011, 07:17 PM
I think I would open the area and look at the plumbing. The others are correct that the system "should" be a closed system but you are sure you have the correct connection in the bay. So either this was a coincidence of the valve popping or something is not plumbed correctly which would be extremely dangerous if the black rinse was connected to any fresh water plumbing. If it were mine I would open the access and check the hookups just to be sure before using any water.