DIY greywater sump tank w. automagic pumpout

Lomax

Lomax

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Being the paranoid type, I have opted to weld up and close off all the through-hulls under the waterline on my boat, other than the water intake for the engine. That means I have to have a discharge pump on the grey water, sucking it up from a sump tank in the bilge and draining overboard. The problem is, the free height between the stringers is only 16cm, and I don't want to fit a tank that sits flush with the inside of the hull as it would become an inevitable rust spot. Leaving an air gap of a couple of centimetres underneath the tank means I only have ~14cm height, and I haven't been able to locate a suitable tank with such a low height. Capacity wise I don't think I need more than 6-10 litres of volume (for example, the small Whale grey water sump is just 8 litres), but it needs an inspection hatch, and preferably a transparent lid. After scratching my head for a while, I came to think of IP67 rated electrical enclosures like this one from Fibox:

fibox5638.jpg

What do you guys think, any reason why this wouldn't work?
 
Well, I think you're excessively paranoid. If you're happy to have one through-hull, why not have several? After all, they're not under any real pressure, and you'd have to be really useless at inspection to risk having one fail.

Regardless, if you're going down this route, there are off-the-shelf solutions. Have you looked at the Whale Grey IC system? The manifold should easily fit in your 16cm deep space. I have a Gulper IC pump on my shower drain, and it works extremely well.
 
Hehe, well, apart from the galley sink, they have all already been welded up (there used to be a pump-out toilet on board as well, with another two through-hulls). The Gulper IC looks interesting - and your positive experience is noted!
 
6 - 10 litres seems a very modest volume for a grey tank. We have galley sink, shower well, and heads WHB going into ours, and while we always use water very sparingly, that wouldn't do for us. (We tend to use quite a lot of sea water at the galley, for veg prep, rinsing etc, and it all goes into the grey tank.)
 
Lomax said:
Do you know what the height of the manifold with 1" connections is?
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Look at the Whale catalogue. The manifold is 114mm high, but then you have to add an elbow for the outlet pipe to the pump. No reason why it shouldn't fit in your space.
 
NormanS said:
6 - 10 litres seems a very modest volume for a grey tank. We have galley sink, shower well, and heads WHB going into ours, and while we always use water very sparingly, that wouldn't do for us. (We tend to use quite a lot of sea water at the galley, for veg prep, rinsing etc, and it all goes into the grey tank.)
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The idea though is to have a pump which automatically operates to remove the grey water. So it wouldn't really matter if the tank were 1 litre or 20 litres.
 
pvb said:
The idea though is to have a pump which automatically operates to remove the grey water. So it wouldn't really matter if the tank were 1 litre or 20 litres.
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Aye OK. I forgot about the automatic bit. I'm old fashioned, and prefer to have control. We tend to pump ours out every second day. (Gulper).
 
Yeah, the idea of the sump is just to act as a kind of "spring", so that the pump doesn't cycle too frequently.
 
Do not do this.

Grey water tank is the nastiest thing on the boat, far worse than the black tank. The main problem is the collection of fats and soaps. It has to be cleaned out often, and it is hideously disgusting.

If you really must get rid of the through hull, then use something which pumps straight out, like the Whale Gulper IC.

If you really want a grey water tank, then buy a Whale IC system and come around, and I'll swap you mine.
 
Thanks - I'll put that down as a second Whale Gulper IC recommendation, an a pretty convincing one too.
 
Sorry, but it's plain nuts to weld up sink sea cocks and then fit pumped systems to get rid of washing up water. Almost every boat on the water has a bunch of sea cocks, it's almost unheard of for a boat to sink through a failed one, unless it doesn't get any maintenance for donkeys years.
 
The outlet from the pumped discharge from our grey tank is several inches above the normal (unheeling) WL, so it's not really even much of a potential hazard. I can think of more serious things to worry about. :rolleyes:
 
You have to be able to open the tank and access the pump. A big screw on lid is the best system. No internal pump ever completely empties a tank, and grey water generates slime that has to be cleaned out regularly or it will clog the pump.
 
NormanS said:
You seem to be determined to make a simple thing difficult!
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And you seem to be determined to troll me with insults every time I post. Do you do this to everyone here, or is this a special honour?

NormanS said:
That design looks good for siphoning water back into the boat in the event of a burst diaphragm in the pump.
Click to expand...

Explain how and why this is any less likely to cause siphoning?

outlet2.png

Ever heard of siphon breaking valves? You may also note that the pump is placed above the waterline, so a failure there will also be above the waterline.

P1020813-M.jpg

Is this you?
 
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