Jabsco bowl empties when tank is emptied

[GWilly]

I have a Jabsco Quiet Flush which I believe to be original to the boat, making it 14 years old. It works fine, no odors, etc. But when I am emptying (suctioning) out the holding tank, any water in the bowl gets suctioned out too. In fact, I can hear the bowl water getting sucked out from outside the boat while I’m attending the suction hose. This doesn’t seem normal but I haven’t found anything in the head system that is failing. No leaks, nothing. Looking for your thoughts, folks. Thanks.

[ranger58sb]

It worked that way on ours too, when we still had original hoses, the inlet from toilet to holding tank was on the side of the tank near the top, and the outlet hose (to dock pump out) was on the side of the tank near the bottom. Didn't seem to hurt anything, didn't seem to impact the joker valve.

Since then, I've recently redone much of that so both our inlet hose and outlet hoses are now on the top of the holding tank... and we didn't seem to get that sucking from the bowl when we pumped out. Have only pumped out once with the new setup, though.

-Chris

[peghall]

Most likely your holding tank vent is blocked. Tank vents have 2 main functions: 1. To provide an escape for air in the tank as it's displaced by incoming contents. If air can't escape, the tank--the whole system--becomes pressurized...and 2. To provide a source of air to replace contents as they're drawn out, without which the pump will pull a vacuum that won't let it pull out more than a gallon or two. So if a pumpout or macerator pump can't pull in the air it needs through the vent, it'll try to find another source...which in your case seems to be the toilet bowl.



So do NOT use the toilet again or try to pump out or dump the tank until you've cleared the vent. Without a source of air to replace contents as they're being sucked out of the tank, the pump will pull a vacuum that'll prevent it from pulling out more than a gallon or two. A particularly strong pumpout can even implode a tank.

The two most common locations for a vent blockage are the vent thru-hull and the other end of the vent line--that end of the hose and the vent fitting on the tank. Start by cleaning out the thru-hull...use a screwdriver blade, ice pick--whatever works. If that doesn't result in a spew out the vent, you'll need to relieve the pressure before removing the vent line from the tank to clean them out...so open the deck pumpout fitting VERY CAREFULLY with a hose at the ready. Be sure you're UPwind of it! Scrape out that end of the vent line and the vent fitting on the tank...replace the vent line.
If there's a filter in the vent line, remove it...once a filter gets wet--which can happen when a tank is overfilled or even due to heeling--the charcoal swells and blocks the vent...one of the reasons why vent filters aren't recommended for use on most sailboats.


If you need more help to do this, I'll be glad to provide it...here or "one on one" via email.



--Peggie

[GWilly]

Thanks, Peggie, that makes a ton of sense. I was down looking over the holding tank recently because the tank level monitor wasn’t working. I snapped a few photos, which shows what I think is the vent hose (smaller hose at far left). To clean out the thru-hull, I assume you’re thinking from the inside of the boat, i.e., removing the hose from the fitting?

[peghall]

Nope...the part that sticks out on the outside of the hull...typically a "cap" with a slit in the bottom or a screen in it (knock it out if there is one...screens cause more problems than they prevent or solve). It's most likely identical to the fuel and water tank vent thru-hulls.



--Peggie

[GWilly]

Thanks for elaborating on that vent thru-hull, Peggie. I’ll check it out today. It’s on the port side of the boat, which faces away from the dock, so I’ll have fun with that. I’ll follow up with what I find/do.

[Scubaseas]

I had a carpenter bee build a nest 14" in from the hull vent. Dock water hose pressure would not flush it out in either direction. Had to remove (and replaced just to get it working) the entire hose to find it. Cut open hose and inside was a dense 3" long mat of fine grass, hair and other junk. I now use screens over every opening of my boat. Boat was on the hard for two years and several hoses had someone move in and set up house keeping.

[peghall]

Screens aren't "clog proof"...dust, pollen and, if they're metal, corrosion...but just air pollution can deterioriate 'em. When that happens, now that the boat is no longer on the hard, an open thru-hull instead of the usual "vent" thru-hull makes it possible to stick a hose nozzle against it to backflush the vent line every time you wash the boat and/or pump out. Also allows a lot better air exchange/oxygen (essential to odor prevention) with the gasses in the tank.


--Peggie

[peghall]

Have you considered turning the boat around to park the stbd side of it next to the dock long nough to clean out the thru-hull and replace the thru-hull?


--Peggie