Is my waste system gravity fed?

capejt · Feb 19, 2013

Gravity works, but...

Yes, gravity systems as you describe do exist. I saw one on a Lagoon 37. The problem with these systems (as I have witnessed first hand) is that they are very very prone to clogging.
Not a pleasant chore to poke a wire clothes hanger up through the thruhull while trying to avoid the deluge of "stuff" into the water. It was like a sci-fi movie avoiding the deadly "fog".

wetass · Feb 19, 2013

Is the bottom of the tank above the water line also? If not, the water/waste will flow the wrong way. Gravity fed systems on sailboats usually have the holding tank in the wall behind a cabinet rather then under a bunk or under the floor to get them high enough to drain.

Chris Patterson · Feb 19, 2013

I can see how the flow past a moving thru-hull could pull the waste out. But like post #2 said, it cannot work THAT well. Just put a pump in it, and that'll solve your problem. You'll have to put an adapter on the thru-hull for a one inch hose though, as that is the common Macerator pump discharge size.
It would be very difficult for what you have to move out solids out of the tank.
What a cheesy setup..

Bob 04 H260 · Feb 20, 2013

I lived on a Beneteau 36CC for a bit. The system works OK. The trick is to not use much toilet paper. If you do it will get a clog. If you get a clog the solution is to put your dinghy air pump hose over the vent pipe outlet (easy to reach from the deck). Seal it a bit with a wet towel, then a small amount of pressure will clear the clog. That was the way it worked for us.
Also keep the waste holding tank empty when sitting not being used they have a tendency build up sludge in the bottom that also clogs things up.
Enjoy her, nice boat, quite fast, Bob

Ron20324 · Feb 20, 2013

galynd said:
... So, would solid waste exit without a macerator? I've heard of gravity waste systems but I'm not familiar with them...

If it's a factory system, I'd say it should, or they would not have made it. Just make sure to use it while moving. If from a previous owner, it's a crap shoot/chute, so to say....

Gunni · Feb 20, 2013

galynd said:
On my Beneteau 36 I do not have a macerator. The toilet will dump into the top of the holding tank or directly overboard through the thru hull valve. The waste exits at the bottom of the tank where you can connect to the deck pumpout. It also Y's to the thru hull valve. The bottom of the Poly tank is approxi1mately 1 foot above the thru hull. There is no macerator. My prevous boat had a macerator above the tank. The hoses are all approximately 1.5 inches. So, would solid waste exit without a macerator? I've heard of gravity waste systems but I'm not familiar with them.

Thanks,
Greg.

If it is like my OEM system waste diverts overboard only when the Y-valve is set to discharge, and only for waste being pumped. Once waste goes into the tank, you have to pump it out through the deck pump-out fitting. As a result, the hose runs are very long (~6' each). And that ain't good.

I'm working up a plan to convert to a system where the tank gravity feeds to overboard discharge through a valve. Per Nigel Calder's Boatowners Manual.

druid · Feb 21, 2013

Just a warning: if there is no siphon loop on that hose between the holding tank and the thru-hull, it's against ABYC standards and water can flow back into the tank and possibly sink the boat. ANY hose connected to a below-water thru-hull should be looped well above the waterline.

I'm going to add this to my system (currently the only way to empty my holding tank is at a pump-out station, and there aren't many on the West Coast). I will add a Y-valve, macerator/pump and siphon loop (actually the siphon loop is already there from when the head pumped directly out the thru-hull).

And double-clamp everything.

druid
"Wind Drift" Ontario 32

Gunni · Feb 21, 2013

Druid;
Make sure you vent that siphon loop overboard too.