Jabsco manual head operation...

[wdonovan]

Issue is holding tank not pumping out. Did some research and census is to suspect tank vent first. My question is: If I lift the handle on the Jabsco pump rather than locking it in the down position, doesn't that essentially allow the tank to vent through the Jabsco unit?

 

[Peggie Hall HeadMistress]

Nope. Pumpout might be able to pull in a little air through the toilet--in fact, a hissing sound from the toilet during pumpout is a big clue that the vent is blocked--but not enough for the toilet to replace the tank vent during pumpout. The best it can do is let enough air escape to relieve the pressure in the tank,which will take some time.

TANK VENTS 101
All tank vents have two main functions: to provide an escape for air displaced by incoming contents and provide a source of air to replace contents as they're pulled out. When air displaced by incoming waste cannot escape out the vent the tank becomes pressurized, creating increasing back pressure that prevents the toilet from flushing.

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.

When air displaced by incoming waste cannot escape out the vent the tank becomes pressurized, creating increasing back pressure that prevents the toilet from flushing.

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 the thru-hull is one that has a screen in it, knock it out...screens cause more problems than they prevent. 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...reconnect 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.

I also recommend that you replace the "vent" thru-hull--which is designed to keep sea water out of the fuel and water tanks, but boat builders use 'em on holding tanks too--with an open bulkhead or "mushroom" thru-hull that'll prevent vent blockages by letting you put a hose nozzle against it to backflush the vent line every time you wash the boat and/or pumpout.

--Peggie

 

[kloudie1]

Peggie, a question.. with the Jabsco pump handle up, wouldn't the pump out pump be able to suck air up through the foot valve , through the joker valve then into the tank to allow pump out? (and maybe not collapse the tank).. Not ideal for sure, but should allow pump out if the vent is plugged? Would certainly not allow venting to provide for additional tank contents.. I guess part "B" is "Why would ya do that instead of cleaning the vent?"

 

[Peggie Hall HeadMistress]

A joker valve that's so worn that the slit has become a hole MIGHT allow enough air to be sucked in via the bowl to allow pumpout...it depends on the routing of the toilet discharge line. But even if it does, pumping out would take considerably longer than it would if the pumpout could pull in air through the vent.

I guess part "B" is "Why would ya do that instead of cleaning the vent?"

My thought exactly. I'd try this only if the tank were so full that the level in the tank HAS to be reduced to no more than half a tank to risk removing the vent line from it...and I'd even do that after the toilet has sat unused for at least 24 hours to allow it to de-pressurize.

--Peggie

 

[wdonovan]

Wow thanks! A ton of info here. Send the job over to the marina because I just didn’t have time or experience troubleshooting. The problem turned out to be the pump out hose had come off the pump out deck fitting nipple. Although it was a pain in the neck place to get to it was not a difficult fix. I need to read Peggy’s post one or two more times Times to get as much information as I can from it. I plan to have the hose replaced that goes from the head to the tank and also the pump out hose. The reason I have to replace that is that there is a PVC octopus connecting all the hoses to the macerator and tank. Since I will never use the boat offshore the macerator is useless and I want it removed. This will allow the removal of this multi T multi elbow PVC contraption and permit running a snake through the hose if it’s ever necessary. When the PVC fitting assembly is removed The pump out hose will have to be replaced with a slightly longer one.

 

[Peggie Hall HeadMistress]

I need to read Peggy’s post one or two more times Times to get as much information as I can from it.

At the risk of being accused of shameless self-promotion...you'll find a lot more information in my book (see link in my signature below). The title (my publisher's idea) is a bit misleading...'cuz although it does deal with every source of odor on a boat and how to cure, or better yet PREVENT 'em, it's actually a comprehensive "marine toilets and sanitation systems 101" manual that explains the laws, describes all the types of systems and how they work, and will help you learn how to operate and maintain your system to prevent 99% of problems instead of having to cure 'em. 'Cuz you get to do any preventive maintenance on your terms when it's convenient...the need to cure a problem never happens when it is! And I'm always glad to answer any questions it doesn't.

--Peggie