Using one thru-hull for heads sink drainage and heads inlet

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yerffoeg

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I am modifyng the heads on my boat and am thinking of blanking off the heads sink thru-hull, and plumbing the sink drainage instead into the heads raw water intake.

The idea of having one less thru-hull is appealing. I am installing a Blake's Lavac toilet. The above change would, however, mean having to shut off the T connection to the sink to allow a satisfactory vacuum to allow the toilet to work.

Your thoughts please.
 
Just one question really, why?

Suggestions though, you could, a valve would do it, but you would have to pump the toilet when you use the sink, just dont see the point, the through hull is already there.
 
So do valves in the lines to your sink, with five extra connections to worry about. But of course it is your choice.
Sorry if I seemed a bit OTT.
 
Syphoning?

In what circumstances might your heads sink through-hull generate a risk of syphoning? Or maybe your sailing's very different from mine?
 
Bit more detail needed... what is the concern? I assume as you talk about "blanking off" the through hull fitting not removing it that it must be the valves that concern you (dezincification etc.).
If they are ball valves then as you're east coast based Volspec (based Tollesbury and a couple of other places) do DZR valves for £5 for 1/2 inch to £10 for 1 inch.
Just replaced mine ...... only connection to Volspec is as a satisfied customer.

Apologies if this is wide of the mark from what you were asking,
Paul.
 
Geoff, I have been using the system you are considering, with a Blakes Lavac, for the past 15 years. Mine is a S/S sink, with a lever-action ball valve immediately below the outlet. No problems and some clear advantages; such as releasing the suction in the heads by a quick flick of the valve instead of waiting until sufficient inflow allows the lid to be lifted without stressing it. Go for it!
 
Good point from Boatbuilder: never considered it. But never had bug trouble in the fifteen years either. I'm not about to change back.
 
Thanks Piotaskipper: I a pretty sure I will go for this option. Boatbuilder's point is not entirely valid. I agree that as a general rule, the fresh water system and toilet plumbing must be kept separate, but the issue being discussed is different. We are talking about joining the heads water intake with the heads basin effluent.
 
[ QUOTE ]
some clear advantages; such as releasing the suction in the heads by a quick flick of the valve instead of waiting until sufficient inflow allows the lid to be lifted

[/ QUOTE ] If a Lavac is taking an excessively long time for the vacuum to be released, or ends up with too much water left in the bowl, you should look at the air bleed in the inlet pipe. They do need a clean once in a while. If a Lavac is working properly it should be possible to follow the Lavac instructions to the letter. You end then end up with just a little water left in the bowl and there is no need to lift the lid again 'til you want to use it again.
 
[ QUOTE ]
Sewage and fresh water must be kept apart at al times , the transferance of bacteria is a great danger, do not couple the two together.

[/ QUOTE ]

Connecting any toilet designed to use sea water to the fresh water system is indeed a very bad idea, and every toilet mfr specifically warns against it. However, connecting the toilet intake to a sink DRAIN doesn't present any danger...in fact, many boat builders use a single thru-hull for both the head intake and sink drain. It's good idea, for a couple of reasons:

1. it eliminates a hole in the boat...2. It provides a means of rinsing the the sea water out of the system before it can stagnate and stink...close the thru-hull, fill the sink with clean water, flush the toilet. Because the thru-hull is closed, the toilet pulls the water from the sink. Just pouring water into the bowl only rinses out the discharge...this method rinses out the intake and the channel in the rim of the bowl too.

It is necessary to either keep the sink plugged when not in use, or install a shutoff valve in a convenient location in the sink drain that remains closed except when the sink is in use (rarely will both the sink and the toilet be in use at the same time)...otherwise the toilet will pull in air from the sink that will prevent it from priming.
 
Yup, quite right. Both my American boats (Tartan 37s ) had this system as standard and it worked very well. That's a through hull hole removed or replaced or whatever!
 
Your proposal also has teh advantage that at the end of atrip you can fill the sink with fresh water, and diinfectant, close the heads inlet and then pump the fresh water through the heads, thereby killing any smelly bacteria in the INLET side of the heads piping.
I am considering using this system, but haven't got time to do it this year!

Regards
 
Generally sinks drain to waterline, heads inlet is well under water.

You would have to use a combined fitting below the level that would come out of the water underway. Depending on how high the sink is, and what angle you sail at, you may risk free flow when hard pressed on one tack, unless you always shut the seacock when underway. The junction of the two, and hence the changeover valve would need to be deep down too.
 
back in this ancient thread.
I have this setup but there is one side effect. Its rather likely that if in the sink there is no water or tap you will rather pump air from the sink than water from the sea.
 
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