Bilge Pumps - Check Valves

Bilge Pumps - Check Valves

Post by Bill Gardn » Wed, 03 Aug 1994 12:00:05


I have a long run of hose on my bilge pump.  When the pump shuts down quite
a bit of water runs back into the bilge.  The answer seems to be to install
a check valve near the output side of the pump.  Are these available in
plastice versions for a reasonable price and is this a practical solution??
 
 
 

Bilge Pumps - Check Valves

Post by Rod Mc Inn » Wed, 03 Aug 1994 23:59:25

Quote:

>I have a long run of hose on my bilge pump.  When the pump shuts down quite
>a bit of water runs back into the bilge.  The answer seems to be to install
>a check valve near the output side of the pump.  Are these available in
>plastice versions for a reasonable price and is this a practical solution??

  Yes, you can get plastic check valves, but the general wisdom says don't do it.
The reasons are:

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
pump useless.

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.

        Rod McInnis

 
 
 

Bilge Pumps - Check Valves

Post by Robert S. Macfarla » Thu, 04 Aug 1994 02:50:08


Quote:

>I have a long run of hose on my bilge pump.  When the pump shuts down quite
>a bit of water runs back into the bilge.  The answer seems to be to install
>a check valve near the output side of the pump.  Are these available in
>plastice versions for a reasonable price and is this a practical solution??

You can get plastic in-line check valves for hose/pipe at West Marine
(and probably other shops); typical costs are $8-$15 depending on the
hose diameter.  Check valves on bilge pump lines receive mixed review;
make absolutely certain the valve is oriented the correct way (that
water goes out of the boat) - Ornaith Murphy had a boat yard set up
check valves on 7 bilge pumps located throughout a Cal-39, and the
yard got 5 of the valves backwards! (this meant the pumps couldn't
get anyway water past the checkvalve, and she almost lost the boat
when a thru-hull fitting failed).

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).

- Rob

 
 
 

Bilge Pumps - Check Valves

Post by Beau Vrol » Fri, 05 Aug 1994 08:15:51

Quote:

>I have a long run of hose on my bilge pump.  When the pump shuts down quite
>a bit of water runs back into the bilge.  The answer seems to be to install
>a check valve near the output side of the pump.  Are these available in
>plastice versions for a reasonable price and is this a practical solution??

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.

Beau Vrolyk, Saga

 
 
 

Bilge Pumps - Check Valves

Post by Michael B. Lai » Fri, 05 Aug 1994 20:45:16


Quote:
>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.

>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).

Another solution is a very small bilge pump with very small hose.  Not ment
as a replacement since you might still need the larger pump if you spring a
serious leak.  By using 1/2 inch hose (or maybe even 1/4) you won't have
much water to back flow.  True, you won't pump very fast, but then most of
the time all you need to do is keep up with the stuffing box.  If you set
the switches up right, the little pump will keep the bilge near dry, and if
a major leak is bigger then it can handle, the big pump will come on.

Mike Laing
S/V Pathfinder

 
 
 

Bilge Pumps - Check Valves

Post by Stuart A. Be » Fri, 05 Aug 1994 21:26:51

: I have a long run of hose on my bilge pump.  When the pump shuts down quite
: a bit of water runs back into the bilge.  The answer seems to be to install
: a check valve near the output side of the pump.  Are these available in
: plastice versions for a reasonable price and is this a practical solution??

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
a time.

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.

/Stu
--

P.O. Box 42                  on board the Shearwater

(202) 287-8715                      

 
 
 

Bilge Pumps - Check Valves

Post by Robert S. Macfarla » Fri, 05 Aug 1994 10:19:36


Quote:


>>I have a long run of hose on my bilge pump.  When the pump shuts down quite
>>a bit of water runs back into the bilge.  The answer seems to be to install
>>a check valve near the output side of the pump.  Are these available in
>>plastice versions for a reasonable price and is this a practical solution??

>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.

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).

- Rob

 
 
 

Bilge Pumps - Check Valves

Post by DFELSENT.. » Tue, 09 Aug 1994 03:20:41

If it were up to me there would be a check valveon every bilge pump on
every boat I am on. I don't want to rant and rave, but....
At two o'clock in the morning halfway between Newfoundland and Nova
Scotia in a charter boat fifty miles offshore in fortyfive degree water
with twelve foot following seas and thirty five knot windsfifty miles or so
offshore I went below only to discover 18" of water over the floorboards.
After much fear and pumping I discovered that the electric bilge pump
that exited through the transom above the waterline was siphoning water
into the bilge, as it was under water enough of the time to keep the
siphon going.
I am a believer in check valves, with all their faults, and in
anti-siphon loops.