1) It adds a restriction, which cuts down the volume of water the pump
will put out.
2) It adds one more thing that can clog, thereby rendering your bilge
3) Because they must operate with very little forward resitance, they
don't shut off (check) very tight. As a result, they leak. While at
first you may be pleased that the water stayed out, it will all leak
back in during the next hour or so.
Another route to go is to install a very small (like 50 gph) bilge pump
in addition to the normal big one. The little pumps use small diameter
hoses (you can downsize to 1/4" if you want to) and so you have a small
amount of water in the little pump's hose that backflows into the bilge.
I put in a checkvalve on my main bilge pump because I have the same
problem you do - my bilge holds all of 4 gallons (you're typical flat
bottomed fin-keel racer/cruiser), and the length of hose leading from
the bilge pump overboard means that a bunch of water flows back into
the b ilge when the pump shuts down. So far I've had no problem with
the valve. I am going to install a little bilge pump on a very short
hose (probably T the hose into the galley sink drain, and put a seacock
on the line which I open up when I want to manually run the small pump
to clean out the bilge at the end of the day).
Beau Vrolyk, Saga
>In my boat, I can't do this because the hull is very shallow (the actual
>hull draft is something like 16-18", with a big fin keel hung beneath
>that goes down 6 feet. The clearance between the top of the keel stub
>(where the bolts are) and the cabin floor is about 6", just enough
>to hold the bilge pump. There's no way I can get a loop in the bilge
>line near the pump that will also go above the waterline - I wind up
>going aft past the***pit before I can loop it, which leaves a long
>length of pipe that backflows into the tiny bilge (all of 4 gallons - I
>know, because when I completely sponge out the bilge from full it doesn't
>quite fill a 5 gallon bucket).
I think a check valve is a mistake - unless it isn't possible for the
water to siphon back. they tend to leak slowly all the time - so rather
than dropping the hose-load back all at once, they dribble it a little at
Tow potential solutions:
1. The seamanlike soulution - put a vented loop in the hose near the
pump. Run the hose straight up, into the loop (above the water line on
all tacks) and down to the drain with no dips or loops. It will drain
completely and only a little will go back into the bilge - and your
surveyer will love you if he/she is any good.
2. My solution - install a second, very small, automatic pump near your
sink - and connect the line to the sink drain above the water line. Just
a few drips of water come back out since the line is small and the run is
short. Normally, only the small pump works (once a day keeps up with my
shaft log when underway). when the big pump kicks on, I know to check
the bilge for problems.
P.O. Box 42 on board the Shearwater
>Can you simply go up from your pump and make a gooseneck? Then the only water
>that runs back will be from the pump to the gooseneck.
7. check valve
9. Check valve