[rcwiegand]

I am on an extended trip and noticed the vacu flush will cycle without flushing.   This may not happen for days then it will begin and occur a few times before it stops.  When this happens the pump cycles about half the time it does with a full flush.   It seems to occur most often in early morning when it is cooler. There is always water in the bowl when it happens.  I recognize there must be an intermittent vacuum leak and looking for suggestions where and how to start.

[Misdirection]

Try to tighten down the large radiator hose clamp at the base of the bowl. Should take a 5/16 socket. That's what puts pressure on the gasket to make it air tight.

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[ReelMagic]

I had a similar issue and it turned out to be the "duck bill"s that move the sewerage from the bowl to the hold tank. There are 4 duck bills (2 on each side of the vacu-flush vacuum pump). When worn they don't close completely all the time which bleeds the vacuum causing the vacuum pump to come back on.M2c

[jclark003]

If no water is draining down it is usually the base basket (4 studs at the base of the unit) the duck bills as previously suggested, or the ball shaft (has an o ring in the shaft). The vacuum regulator can also leak. If you turn off ac's refrigerators, etc you usually can hear the leak if you listen closely to the head base or down by the pump.

Troubleshooting guide:

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[TIARA44]

Hi,

I just changed the ball shaft assy. I could actually hear the vacuum leak with a mechanics stethoscope - very handy to have on the boat.

Ken

[rcwiegand]

I think it is the duck bills. I cannot hear a leak and we when changed the treatment from the thicker blue aqua chem to green TST which seems to be thinner, the intermittent pumping stopped. Thanks for the suggestions and help.