Why is there an Aft head and shower sump

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Dave_E

Dave_E

Senior Member
Joined
Sep 2, 2014
Messages
276
Location
USA
Vessel Name
Agnus Dei
Vessel Make
36' Shin Shing
Hi All,

Our boat has a small open holding tank aft of aft head with the shower and sink draining into it. There is a float and small bilge pump that shoots everything out the back of the boat above the water line when the level gets up.

I've never seen anything like this. What's it purpose? Anyone else have something like this?

Dave
 
That is a sump system. It is used to pump gray water out of the boat when the shower or sink is near or below the water line. Very common. I have two on my boat, one forward and one aft. The only thing going into it should be gray water.

They do require periodic cleaning since hair and soap scum will clog it up over time.

Both of mine are "open" but some versions come with plastic lids.
 
Last edited:
Dave_E said:
Hi All,

Our boat has a small open holding tank aft of aft head with the shower and sink draining into it. There is a float and small bilge pump that shoots everything out the back of the boat above the water line when the level gets up.
Click to expand...

It should not be "open". There should be a clear plexi cover screwed down with a gasket sealing the sump box. The lid is removable in order to service the pump and clean the strainer.
 
Some are open (the two on my 1989 Silverton Aft Cabin were open).
 
Often open can act as a backup bilge pump... or more often to allow overflow the soap scum and other gray water to you whole bilge
 
That is very common. Our boat also has two, fore and aft, because the floor of both showers is below the water line so they wouldn't drain by gravity. The air conditioners also drain condensation water into those sump boxes. I am surprised anybody's are just wide open though -- I wonder if the tops or lids are just missing. Seems to me at the very least that would prevent gray water sloshing out of the boxes into the bilge in rough seas.


(They would act as kind of back-up bilge pumps if the water ever got that high, the tops aren't that tight and there's a notch where the A/C lines go in -- but then if bilge water ever got that high I'd be reaching for the PFD's and distress flares.)
 
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Our shower sump, in our 1984 boat, is open (a loose cover) but is quite deep. There would have to be about 12" of water in the bilge for the sump to operate as a back-up bilge pump. And that would be a LOT of water! Similarly, there would have to be about 12" of water in the shower sump before the bilge pump could take over. I made a new 3/4" plywood cover for the sump to replace the 1/2" thick one that had been left elsewhere in the boat. Makes grovelling in the forward part of the ER less uncomfortable.
 
As others have mentioned, I have one (with cover) in the forward part of the boat, that grey water from the 2 head sinks, the shower, the AC condensate, and the drain from the chain locker empty into. About once a month it gets filled (with the pump off) with water and a splash of bleach. This eliminates any growth and keeps it smelling clean.

Ted
 
... and because of the debris included in grey water, I learned this is a place where it is easy for the sump float switch to fail due to gunk. In our case it failed in the ON position, so if you ever hear that pump come on and stay on.... its probably time to clean or replace the float switch to that sump.
I had a mechanical float but next time i'm thinking of going with one of those new electronic switches with no moving parts in there.....
 
You definitely want a shower sump. The smell from the shower sump can be as bad as the black water holding tank if not cleaned regularly. When we bought our boat the sump was almost filled with a gray slimey jello like substance. Nasty. Cleaned it out and the bilge smelled much better.
 
Ours is open at the top. Can hold 5 gallons since I made it from an old red gas can.
It only has a 300 gph Rule pump inside, so things would be pretty desperate if it was helping keep the boat afloat!

Advantage of open is also easy to clean out if needful.
 
My 1981 IG has a square f/g sump box with flipper switch and an oversized pump(2000GPH) which appears original. Water from the galley sink,shower, and head washbasin drain to it. The pump has a 3 way breaker switch on the panel. The top panel of the sump box is screwed on, the panel has an opening to accommodate the upper part of the pump. It works well, though we had to revise the degraded 36yo wiring.
 
Our Hatteras had three uncovered sumps, with full size Rule 2000 bilge pumps. They were designed to act as a back up to the adjacent bilges, though I felt the forward one was too high to be the only back up for that bilge. I found the install it and forget it switch solution was the Ultra Pumpswitch. Some of the "solid state" type switches can have issues if they get too scummy, at least a couple people I know had that experience.

I poured some distilled white vinegar down the shower and sink drains on a regular basis and that kept the smell away and cut down on the scum build up. Fine mesh covers over the drains keep the hair issue down.
 
kthoennes said:
That is very common. Our boat also has two, fore and aft, because the floor of both showers is below the water line so they wouldn't drain by gravity. The air conditioners also drain condensation water into those sump boxes. I am surprised anybody's are just wide open though -- I wonder if the tops or lids are just missing. Seems to me at the very least that would prevent gray water sloshing out of the boxes into the bilge in rough seas.


(They would act as kind of back-up bilge pumps if the water ever got that high, the tops aren't that tight and there's a notch where the A/C lines go in -- but then if bilge water ever got that high I'd be reaching for the PFD's and distress flares.)
Click to expand...
Open on our Defever 44, factory original. So, not uncommon at all it would seem.
 
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