Head plumbing details

[InetRoadkill]

I'm working out some of the mechanical systems for a 37' sailboat design I'm toying with. The topic of the day is the head. I have a nice layout for the bathroom but I'm not sure about a couple of things and could use some recommendations.

First, due to the shape of bathroom, there's not enough room to bend the pipe from the toilet outlet to the holding tank without using a 90deg elbow on top of the tank. I'm worried that using an elbow might be a source for clogging. Thoughts?

Second, I would like to keep the bathroom simple and minimize the number of valves involved in using it so that I won't have to give a technical course in boat plumbing every time someone new wants to use the head. With that in mind, I'm thinking about just having the toilet go straight into the holding tank without having a y-valve for directing waste overboard. The holding tank itself would be fitted with a macerator pump to allow draining periodically when out to sea. Granted, this is a minor simplification, but there's not a lot of space for a valve anyway. Comments?

[El Sea]

Installing a manual operated head:

raw water supply approx 1/2" dia - a thru-hull fitting with a seacock (valve), hose routed above water line (when boat is heeled) with a anti-syphon valve at high point, then routed to water inlet connect at head.

Pump Discharge approx 1 1/2" dia - a hose routed to holding tank, (optional) a diverting valve with hose routed to second seacock and thru-valve.


Keep it simple & user friendly.


Good Luck,

El Sea

[rasorinc]

Have you considered a composting toilet? Some are Coast Guard approved.

[El Sea]

My experience with composting head is the space required which can be rather restricting on a sailboat.

[InetRoadkill]

Simple is good. Less to leak or go wrong.

The head is really tight on space. Even though the boat is a fair size, I crammed the head into a rather confined area to make extra room for the more enjoyable areas on the boat. I would like the arrangement to be neat and not look like a rat's nest of plumbing stuffed behind the toilet. Fortunately, I have a 3d modeling program to help out which is how I found that the pipes were going to require a lot of bending to make them fit.

[InetRoadkill]

Hmm, I was doing the google and found a thread over on sailnet.com which asked essentially the same question as this thread. One solution recommended that the toilet go straight into the holding tank without an anti-siphon loop. The vent on the holding tank acts as the anti-siphon. This seems like it would work, but it goes against the recommended installation instructions for the Jabsco toilet.

[El Sea]

It appears that you are confusing the line the anti-siphon goes on. The a/s goes on the raw water supply sa as to keep from flooding the vessel with incoming water.

[InetRoadkill]

Nope. I went back and double checked. They want an anti-siphon on the discharge line when the top of the holding tank is above the toilet discharge outlet.

page 4, figure 3:
http://www.jabsco.com/files/29090_-_29120_-_3000_datasheet.pdf

It seems to me that you would have to completely flood the holding tank before there would be any risk of siphoning. If you did flood the tank, the anti-siphon device is probably not going to save you from back filling. If it did back fill, it would stop as soon as the vent was uncovered again.

[alan white]

I don't know if this is an original idea, but it worked on my cruiser for a few years and worked well.
It goes like this: There is a valve above the through-hull. It is a three-way valve.
This offers two passages, one from head to tank, and one from tank to ocean. The head is piped to the three-way, but it cannot empty directly into the ocean. The holding tank is also connected to the three-way and it can only empty into the ocean.
(One should also have a seacock between the three-way and the through-hull).
Advantages are: No vented loop, no coast guard problems because it's impossible to empty directly into the sea--- you have to fill the tank first and then drain the tank in sequence, and if the toilet,s usable, it has to be going to the tank.
No pump is required to empty tank if the tank is able to drain by gravity.
If three-way clogs (this happened very rarely): Rotate handle to snip obstruction, and repump from toilet to tank.
I'm surprised I haven't seen this system elsewhere. You can't be illegal with it, and it never stinks cause it has no vents inside the cabin. It's dirt cheap because it has just one valve (which should be a minimum 1 1/4"), and it's just about trouble-free.
You might think the gravity draining tank would not empty easily, with frequent clogs. In three years, I had one or two clogs, and I just redirected the valve and pumped the clog backwards into the tank, after which it drained as usual.

[Boston]

what ever happened to the days of a bucket under a lid

soooo
dumb question
if the tank has to get kinda full before it will drain effectively
what happens to the occasional burp of swamp gas

[alan white]

Like aqll good tanks, there is the vent tube, led to the exterior.