head question

Dil

.
Jul 13, 2020
38
Hunter 30T Neptune
new to marine heads having an issue with the water in the toilet filling back into the bowl. I do not use the raw water intake and only use fresh water from the shower. Everything pumps out when I pump the handle but leaks back in. I have tried lubrication. I assume this must be a bad valve?
 
Dec 2, 1997
8,129
- - LIttle Rock
I'm guessing the problem is a blocked holding tank vent that's pressurized the tank, creating back pressure that's not letting flushes make it into the tank.

TANK VENTS 101
All tank vents--water, fuel and waste--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 in a holding tank 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.

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...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.

You've said you're new at dealing with marine toilets and holding tanks...I think you'll find my book (see link in my signature below) very useful. 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
 
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