The dreaded potty burp, can't eliminate it

You said the vent is clear but, did the pipe slide down into the tank?

My old fifth used to do this. It had a curved pipe and when getting full it seemed like the tissue would start backing up in the pipe. It would burp and when this happened I know it was time to dump although if I "pushed" it like you did, I would get a couple more days.

It does not appear that the vent pipe has moved. I went onto the roof to snake it and all looked normal.

Are the vent pipes just clear pipes without any type of one way diaphragm type of valve?

The toilet pipe does make two 45's but snaking the pipe did not bring back any tissue or 'other' things.

Tank burps when empty after dumping and cleaning.

Tank burps when empty after dumping and cleaning.


That is a blocked/obstructed VENT line.

UNLESS toilet line to tank is NOT emptying

Go to Home Depot/Lowes/ACE Hardware and purchase a 'Drain Blaster'
Screws onto a garden hose, push it down toilet line and turn on water. It will expand to size of line sealing it and then blast away with high pressure clearing out line.
Then if toilet stills burps.try it on vent line from roof

They have 3 sizes...get the 1 1/2" to 3" model

Old-Biscuit wrote:
...push it down toilet line and turn on water. It will expand to size of line sealing it and then blast away with high pressure clearing out line.....

and pray it doesn't blow the pipes apart and cause further damage. You take a big risk using that thing.

OP - it sounds like the vent pipe is clogged, are you certain you checked the correct vent?

Agreed that it has to be the vent pipe. I'm pretty sure I got the right one but will re-evaluate today.

I have used the drain busters before but not in an RV.

I'd also try cleaning the tank back to factory fresh, factory clean by using some Liquid Drano and seeing if that helps. Will need to drive a little to make it slosh around. A thorough flush & clean every time you dump may help using an in-tank flusher, wand and/or backflush elbow. You might try taking a hose up onto the roof and putting water down the vent pipe (with valve open) and seeing if it backs up.

We used to have a problem with a pyramid at first until we figured out we needed to add a few gallons of water before using and doing a good flushing/cleaning job before heading home after a weekend trip. Our toilet pipe drops straight down into the tank and is very short. We also use Liquid Drano once or twice a year and it doesn't attack plastic or metal (including seals).

Some tanks are simply harder to dump and flush due to their size, shape and outlet location on the tank and take more effort to clean regularly.

myredracer wrote:
I'd also try cleaning the tank back to factory fresh, factory clean by using some Liquid Drano and seeing if that helps. Will need to drive a little to make it slosh around. A thorough flush & clean every time you dump may help using an in-tank flusher, wand and/or backflush elbow. You might try taking a hose up onto the roof and putting water down the vent pipe (with valve open) and seeing if it backs up.

We used to have a problem with a pyramid at first until we figured out we needed to add a few gallons of water before using and doing a good flushing/cleaning job before heading home after a weekend trip. Our toilet pipe drops straight down into the tank and is very short. We also use Liquid Drano once or twice a year and it doesn't attack plastic or metal (including seals).

Some tanks are simply harder to dump and flush due to their size, shape and outlet location on the tank and take more effort to clean regularly.

You may wish to review what that Liquid Drano really is. The MSDS shows it contains lye and other corrosive materials. It definitely isn't friendly to metal pipes.

westend wrote:
You may wish to review what that Liquid Drano really is. The MSDS shows it contains lye and other corrosive materials. It definitely isn't friendly to metal pipes.

Our KZ onwers manual says to use Liquid Drano.

This Drano info. says "Safe for plastic, PVC, metal pipes, garbage disposals, and septic systems." Drano says all of their products are safe for plastic and metal pipes here as well. The Liquid Drano Max Gel that we've used says safe for metal and plastic right on the label. Does have lye in it but also bleach, a corrosion inhibitor and a proprietary ingredient. The MSDS sheet doesn't say anything about being safe or not on plastic & metal.

A google search shows 6 different types of Drano in a liquid form - Drano Max Gel, Drano Liquid, Drano Max, Drano Clog Remover, Drano Pro Concentrate and Drano Max Build-up Remover. I didn't know there are so many but all are supposed to be okay on plastic & metal. Have also used Liquid Plumr and it said on the label it's safe for metal and plastic label as well.

Here's our problem on our MH, we have the dreaded burp, and the small geyser of water that goes with it. Our tanks our as clean as can be expected and it burps usually after a couple of days of use, indicating waste gasses. Suspecting the vent was blocked, I ran a hose to the roof and it flowed right through. Or so I thought.

Turns out the black and gray vents are combined at some point between the roof and tank, so all that water went into the gray tank and backed up into the shower pan! Yikes!!! I quickly turned off the water and opened the valve before it overflowed.

Since I have no idea where the wye fitting is, how can I check the vent to the black tank? Any ideas?