Waste management

[Guest]

We have a holding tank which deals with the wc in the heads. But galley sink and heads basin and shower all drain into the bilge (which is deep and about 2 cubic feet), to be pumped out with bilge pump above waterline. I'm sure that this will be impractical and smelly so I thought that if I made a box to fit into the bilge containing an electric pump with float switch - all this grey water could be automatically pumped into the holding tank. I envisage the box being sealed to prevent smells and as small as possible (just pump, float switch and about a pint or two) so as not to take up all of deep bilge.

Is this a practlcal idea?

PS - galley etc can't drain direct to holding tank

 

[ccscott49]

I think sowester or somebody makes exactly what you are looking for, plastic box, strainer, pump, float switch and all sealed, ideal for you!

 

[hlb]

Well you cant seal the tank, or you'll create a vaccum, so need a S bend in a breather pipe. (Like at home). Think you will need much more capacity than a pint or two. You need more capacity than the pipe work for a start or it will just pump it half way up and stop, then it will all run back again. Think about it!! Can you not just send sink and shower water straight over the side. Mine dose. My holding tank would be full about three times a day if sinks and shower run in to it as well.

Haydn

 

[ToMo]

All this from someone who believes that a hammer is too high tech for him!!!
<G>
TôMö

 

[HaraldS]

Such boxes are on the market from Rule and Attwood and probably a few more. Have heard that they need a lot of cleaning maintenance and break quite often.
Also, they are not a holding tank, the capacity is small so that you are forced to pump out when showering or using the sink.
Najad's solution to this is that you pump out the shower direct, without an intermediate tank, via a small diaphrame pump. In this case a Jabsco 37202, which can run dry.
I have extended on that solution and had them put in a Y-valve between shower sump and wash basin, so that I now have a pump for each heads compartment which can selectively pump the basin or the shower and two big holes and seacocks less in the hull.
Both have a strainer that I need to clean about once every 4 weeks of usage. Not a big deal. If I had to retain the grey water, it would be easy to divert the output to one of the holding tanks.
We have the Y-valves usually set to drain the washing basins and when somebody uses the shower, he turns it to shower temporarely and back to the basin. If the pump is not running, the basin fills without having to close the drain, which is quite convenient. I'm very happy with that solution, it is clean and it works well.

 

[MedMan]

We have a system something like you describe. Sink, washbasin and shower all drain by gravity into a 'sump' box low down in bilge. This is an off-the-shelf unit made by Whale for the purpose. It holds a couple of litres only. Grey water is pumped from here into a flexible Grey Water Holding Tank. The grey water from this tank is used to flush our Lavac loo so that we do not have any salt water to clog up the pipes leading to and from the loo - a common problem. Outlet from loo goes to Black Water holding tank which lasts us about 3 days before it needs pumping out.

Does it work? Yes, provided we look after it all. The only problem is balancing the amount of water in each part of the system - running out of flushing water at the wrong moment can be unpleasant! The other problem is that the grey flushing water can pong a bit in hot weather. We cure this by putting a 'blue brick' in the sump box. This gives us sweet smelling blue flushing water just like at home!

Have fun.

David

 

[Guest]

Thanks very much for your replies. I have since looked at Tek Tanks catalogue and they make what they call a GWS (grey water system) tank which contains a pump control system, sensor and relay to operate a discharge pump situated outside the tank. They recommend a "diapgragm" type pump with a large bore 25mm - 38mm to go with this tank. But I have just spoken to them and they also supply a tank similar to the Whale tank mentioned, made in USA by Attwood (with float switch and pump inside). HOWEVER, the man from Tek Tanks said that grey water must not be put into a holding tank used for the heads because the soaps upset the bacterial action and cause blockages. I must therefore rethink. I don't really want a separate grey water holding tank. I think that maybe the Attwood tank and pump (about £80 plus vat) will be ok for the shower and heads basin - with a loop back to seacock, and galley waste can go the same way unless it proves too much for it and blocks it, in which case it can go directly overboard below waterline.

 

[ccscott49]

I like the idea of using shower/sink water for flushing the toilet, I've never heard of that, you're giving me ideas! Thanks.

 

[Guest]

After reading your question and the replies I somehow think that you are all missing the aim of a holding tank. The LAW requires you not to discharge grey water close to land and if you do so in the Med some countries will fine you very heavily if you even put bubbles in the water - do you want to swim in dirty washing up water? To stop this happening you need as large a holding tank as possible. In practice most of us livaboards discharge our waste over the side unless in a marina, harbour or swimming area. In this case we hold on to it until we leave (or discharge it illegally at night so that all traces have gone by morning but I will deny this fact in court!!). I have 25 lt. plastic tanks (vented to let the air out) for gally and shower which is enough for a day and a small, SWITCHED bilge pump discharges them . A diverter valve can be fitted to discharge directly over the side when away from land. As for cleaning, bilge cleaner once a year seems to work well.

Hope this brings and makes some sense.

David J

 

[Mirelle]

Yes. A small point, but with a holding tank of this sort of size, as opposed to a tiny one, it is hardly worth using an electric pump; a manual one does the job. Our "below decks" bilge pump (there is a cokpit one as well of course) has a diverter valve for grey water; so far we have never found this a hardship! And one can fit a decent diameter of piping, and seacock.

 

[Guest]

Hi

I am just returning to sail after years of motorboating and the practice that you describe is used commonly on power boats.

For instance the showers and bidets, yes I know !, of my current motor boat drain into what looks like a battery box in the sump which then gets pumped out by a float switch controlled bilge pump.

There are no new ideas in boating !

Good luck !

Steve