Toilet Burping

[Dick Simonis]

This crappy problem just raised it's ugly head.  Periodically, when flushing the toilet it "burps" back.  This is not a good thing and I would really like to resolve it.  How on earth can you generate a positive pressure in a tank vented to the outside?

[Joel Ashley]

With a plugged vent.

[Edward Buker]

Plugged vent as Joel stated or a tank that is full enough that the stand pipe that goes into the tank from the toilet is immersed so that what you flush cannot take advantage of the vent pipe. It may be that the pipe from the toilet does not terminate at the top of the tank. With a flashlight you should be able to see if the liquid level is within the stand pipe or not with the ball valve open.

Later Ed

[Dick Simonis]

Right now the holding tank is empty and flushed.  How can a vent get plugged as it should terminate flush with the tank top???  Still burping.

Guess I should take a water hose to the roof and see what happens.

[Gerald Farris]

Dick,
Be very careful using a water hose on the vent pipe. If you pressurize the tank with a water hose, it can and will cause the tank to split necessitating complete replacement of the tank. If you are certain that the tank is empty, you have a blocked vent.

The best way to clear a blocked vent is to remove the vent cap and use a rod on straight vent pipes or a stiff cable on vents with a turn, to clear the blockage.

One more word, the vent pipe on almost all coaches runs a few inches into the tank so if your tank is full or close to it, your vent pipe will be blocked and the toilet will burp when flushed.

Gerald

[Dick Simonis]

Thanks Gerald,

I guess the first order of business it to pop the access cover and see if the vent is straight.  I did fill it up once so perhaps that is the cause of the problem but one would think that the mere act of dumping would pull enough air in to clear a blockage.

As far as using a hose, if the dump valve is open wouldn't that prevent pressurizing the tank???

Dick

[Edward Buker]

Dick,

With the drain valve open and the water flow at around 35lbs of pressure out of a standard hose you should not be able to pressurize the tank. When you said that the drain valve was open one could envision gases from the campground system perhaps having enough pressure at times to begin to cause your symptoms. Not likely but perhaps possible. I assume that the valve was closed when you had the problem, if not I would close it to isolate that source as being a contributor and recheck for the burps.

Regarding using a hose on the vent pipe, you can spray some water in and check for flow with the drain open as you suggest. I'm not sure that I would try and pressurize it with water to try and clear a blockage. I would vote for a mechanical means of clearing it as Gerald suggests if it is seriously blocked and does not clear with some standing water in the column from a controlled spray dose.

Later Ed

[Ken Buck]

Dirt daubers and other critters seem to like to build nests in vent pipes. Happens a lot on boats, and RV's are no different. Run something stiff down the pipe and knock it out. I carry a piece of 12/2 house wiring for things like this. It's stiff but will with proper coaching go around some corners. It also doubles as a fish wire for those times I need to pull something thru. I know I could buy a regular electricians fishing tape, but that would take the McGyver fun out of it all.

Ken

[Dick Simonis]

Update!!

First, the dump valve has been closed, I was thinking about opening it to flush the vent stand pipe.

I popped over to wal mart this morning and picked up a snake.  5 minutes later the vent was clean and than a plunger to assist the stuff that would drain to the tank due to back pressure.

All seems well for the moment.

NOTE TO SELF:  Do not let the tanks get past 75%. Also, ensure snake and plunger and not buried in the bays.