Jabsco Head Bubbles After 'Flushing'

[Fullmoon]

That pretty well explains it. Pump it until waste gone, pump fresh water in for maybe 6/8 pumps, turn to dry. Bubbles start coming up and sometime colored water. ???

[motion30]

Acts like the vent is restricted pushing air back up the waste line

[Fullmoon]

Thanks for reminding me. We had to do that before when we were forced to over fill the tank before we could get out to empty it.

[webejammin]

Next time your pumping out pump water in the toilet and leave it, it will suck the vent clear and not suck air thru the toilet. it works for us

[peghall]

You've just been VERY lucky! That would not dislodge a mud dauber nest and prob'ly only opens up very narrow passageway that barely allows enough air to pump out the tank. One of these days it's not gonna work and strong pumpout will crack the tank.

What you do you have against just back flushing the vent line every time you wash the boat? If the vent thru-hull doesn't allow that, replace it with one that does.