Problem at pump out

[frank arndorfer]

Peggy, recently I've been having a problem getting my holding tank completely pumped out. I have a Hunter 426DS equipped with dual vacu flush heads. The last two times we pumped, it simply wouldn't completely empty the tank. The gent at the pump out station mentioned possibly the vent may be plugged. If so, how does one unplug the vent...compressed air.????reason I'm believing it's not completely emptying is reading the gauge...which is the highly recommended Snake River Accugauge. Also I can tell by just how much waste water I see in the evacuation hose. We've kept this tank and toilets meticulously clean (or at least have tried to). Any suggestions.???

 

[Peggie Hall/HeadMistress]

Sounds like blocked tank vent to me

Fwiw, your holding tank has nothing whatever to do with the type of toilet...a VacuFlush is just a toilet that flushes into the tank, same as any other toilet does. The suction pulls the waste as far as the vacuum pump...the vacuum pump pushes it the rest of the way to the tank or a treatment device.Do not try to clear it with compressed air...you could damage the plumbing before the blockage lets go. First, look for a kink in the vent line. Most holding tank vent blockages occur at the thru-hull...insects, dirt dauber nests, tank overflow while heeled can plug it up very easily. Scrape it out with screwdriver blade. If you don't find anything in the thru-hull, remove the vent from the tank and check the vent fitting. Even if you never overfill the tank to overflowing, heeling can send waste into the vent line, creating a buildup that will eventually plug it.If there's filter in the vent line, and if waste has flowed out the vent, the filter may be clogged. Filters are toast immediately if they ever get wet anway, so they make it impossible to keep the vent clear by backflushing it when you wash the boat...replacements are $50+ each...and they only last a season even if they don't get wet. So you have nothing to lose and everything to gain by getting rid of the damn thing. Don't use the head or attempt to pumpout or dump the tank again until you've cleared the vent. Flushing against a blocked tank vent will pressurize the tank--which can have all kinds of nasty consequences, from a waste bath to a cracked tank...attempting to pump out against a blocked vent causes the pumpout to pull a vacuum that can crack the tank. Btw...my book includes an entire chapter on holding tank vents and how to maintain 'em...see the link below.

 

[Jim Rushing]

Be Aware

that your Snake River Gauge might not be calibrated correctly. Has it shown empty and full correctly in the past? I just replaced my sending unit this spring and I am still going through the calibration process. I need to cut some of the foil off the bottom according to Dennis.

 

[Terry]

Hi Frank, here is what I do to our 1991 P42...

I made a special adapter that I attach to a water nozzle that fits over and seals the tank vent scupper. After I flush the holding tank until clear water comes out I squirt water under pressure, because of this special adapter, through the vent scupper. I can feel whether water is flowing through the vent line, which tells me if it is clear or not. Then I flush the tank one last time. I had a series of minor holding tank problems that I've cleared up. The systems now works great. BTW I always keep the through hulls closed until I need to use the heads.I also always flush a gallon of fresh water through each head before the last tank flush to make sure only fresh water is in the discharge line. I follow that with one quart of water with Odorlos.Terry