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Old 23-03-2012, 04:26   #1
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Two Bilge Pumps on the Same Hose

I do not have place for another hose for bilge pump (manuel). so my question is if it is possible to mount electric bilge pump on the same hose as manuel pump is mounted on?
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Old 23-03-2012, 04:40   #2
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Re: two bilge pumps on the same hose

Generally it's a bad idea..... because the way I see you doing it might require a check valve in the line after the electric bilge pump (if centrifugal).
While many will argue that a check valve is no big deal...well....what can I say....they are wrong!

If you are gonna do it another way..post it..I'd be interested.
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Old 23-03-2012, 06:02   #3
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Re: two bilge pumps on the same hose

Quote:
Originally Posted by amarf View Post
I do not have place for another hose for bilge pump (manuel). so my question is if it is possible to mount electric bilge pump on the same hose as manuel pump is mounted on?
I'm considering the same thing. I think I'll install a manual Y-valve to select between the two pumps. I wouldn't be able to run both pumps simultaneously, but that wouldn't make sense anyway when both are on the same hose.

Anything wrong with this idea?
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Old 23-03-2012, 06:17   #4
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Re: two bilge pumps on the same hose

Depends...but if neither pump is submerged, the pump that is pumping will suck air through the pump that is not running as soon as the least bit of water is pumped.

Bill
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Old 23-03-2012, 06:22   #5
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Re: two bilge pumps on the same hose

Quote:
Originally Posted by Ziggy View Post
I'm considering the same thing. I think I'll install a manual Y-valve to select between the two pumps. I wouldn't be able to run both pumps simultaneously, but that wouldn't make sense anyway when both are on the same hose.

Anything wrong with this idea?
This is the way I would go, providing the Y-valve is a quick and EZ access and the pumps were two different locations.
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Old 23-03-2012, 06:23   #6
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Re: two bilge pumps on the same hose

Quote:
Originally Posted by amarf View Post
I do not have place for another hose for bilge pump
For the same reason I have two electric bilge pumps Y connected to two manual bilge pumps connected in serie. Keep the common hose to the largest size.

Quote:
Originally Posted by chala View Post
Some bilge pumps come with check valve inbuilt.
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Old 23-03-2012, 06:50   #7
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Re: two bilge pumps on the same hose

ABYC Section H-22.8.8" states:
"If the discharges of several pumps are manifolded to discharge through a single thru-hull fitting, the system shall be designed so that the operation of one pump will not back feed another pump, and the simultaneous operation of each pump will not diminish the pumping capacity of the system. A check valve shall not be used in the manifold discharge system.

See also ➥ Manifolding Multiple Bilge Pump Discharges
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Old 23-03-2012, 09:35   #8
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Re: two bilge pumps on the same hose

Quote:
Originally Posted by GordMay View Post
ABYC Section H-22.8.8" states:
"If the discharges of several pumps are manifolded to discharge through a single thru-hull fitting, the system shall be designed so that the operation of one pump will not back feed another pump, and the simultaneous operation of each pump will not diminish the pumping capacity of the system. A check valve shall not be used in the manifold discharge system.

See also ➥ Manifolding Multiple Bilge Pump Discharges
IAW two 1/2" pumps would have to go into a 1-1/4" discharge hose. And the pumps them selves would have to resist back pressure, or have such a static head that the water could not back up into the manifold/other pump(s).
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Old 23-03-2012, 10:00   #9
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Re: two bilge pumps on the same hose

When we HAVE to do this we use a Y fitting (not a Y valve) with separate anti siphons on each pump. So, the pumps run up to their anti siphon valves and down into the common Y (which is large enough to handle full flow from both pumps at once) and to the discharge.

IMHO, bilge pumps are a critical safety feature, not an area to to skimp on with either materials or installation.

Scott
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Old 23-03-2012, 10:38   #10
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Re: two bilge pumps on the same hose

Quote:
Originally Posted by delmarrey View Post
IAW two 1/2" pumps would have to go into a 1-1/4" discharge hose. And the pumps them selves would have to resist back pressure, or have such a static head that the water could not back up into the manifold/other pump(s).
Double a hose's diameter, and you quadruple it's capacity.
Hence, a 1" diameter hose will have a capacity equal to 4 hoses at " diameter.
Accordingly, a 3/4" diameter hose will handle 2 (actually 2.25) hoses/pumps at " diameter.
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Old 23-03-2012, 11:04   #11
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Re: two bilge pumps on the same hose

Ummm...manual bilge pumps and some electric pumps have two check valves built into them. So how bad can they be? Just saying. Such are rules...

However, I agree that one should not share outlets on bilge pumps that are expected to keep the boat floating when something goes wrong. There's always room for another hose. Get out the SawsAll.
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Old 23-03-2012, 11:30   #12
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Re: two bilge pumps on the same hose

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Originally Posted by Ziggy View Post
I'm considering the same thing. I think I'll install a manual Y-valve to select between the two pumps. I wouldn't be able to run both pumps simultaneously, but that wouldn't make sense anyway when both are on the same hose.

Anything wrong with this idea?
Aside from other problems pointed out, this also reduces your potentially pumping capacity. You won't BOTH pumps fully functional at all times. You might just need them both.
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Old 23-03-2012, 11:43   #13
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Re: two bilge pumps on the same hose

"if it is possible "
Anything is possible. The question is, whether you are making the boat safer and more reliable, or just more complicated and likely to have problems?

We had a similar problem on finding the excellent manual bilge pump (mounted in the cockpit wall) had no intake hose, and no way to run one into the bilge. So we ran the hose under the galley, left about a 6' long coil of hose under the galley with a nice bronze strum box on the end, and if the manual pump has to be used, you lift a floor board, drop the hose into the bilge, and pump away.

There is no need to have the fat emergency hose permanently deployed. Even if we don't pull it over to the bilge, it will still work except for the last foot of water in the hull, which is damned better than nothing.

I'd strongly suggest: Two pumps, two hoses, zero check valves. Check valves ALWAYS jam or leak, the only question is how badly and when. Two pump system are redundant. Shared parts between them, are just begging for a common failure mode to take them both out.
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Old 23-03-2012, 11:49   #14
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Re: two bilge pumps on the same hose

Quote:
Originally Posted by GordMay View Post
Double a hose's diameter, and you quadruple it's capacity.
Hence, a 1" diameter hose will have a capacity equal to 4 hoses at " diameter.
Accordingly, a 3/4" diameter hose will handle 2 (actually 2.25) hoses/pumps at " diameter.
You are right!
I just like to compensate for the reduction of hole size for a bronze thruhull fitting and all restriction of the other fittings, with room to spare. The inside of a hose is not necessarily the smallest orifice in a system.
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Old 23-03-2012, 12:24   #15
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Re: two bilge pumps on the same hose

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Originally Posted by hellosailor View Post
... I'd strongly suggest: Two pumps, two hoses, zero check valves. Check valves ALWAYS jam or leak, the only question is how badly and when...
Indeed!
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