Proper plumbing of bilge pump?

[Moody Blue]

On my to-do-list I need to install and plumb the bilge pump.

Have an 1100 GPH pump with 1 1/8" outlet hose size. Have the 1 1/8" discharge fitting already installed on the starboard side gunnel about 4" below the rub strip.

What is the right way to route the hose between the pump and the discharge? It is a straight distance of about 3 1/2ft.

If I run the line direct (no traps etc), all the water in the hose length will run back into the bilge when the pump shuts off so the bilge will always have a few cups of water in it. If I incorporate a trap, will it result in an airlock and prevent the pump from moving water?

 

[kandil]

Re: Proper plumbing of bilge pump?

You need a back flow chek valve

 

[seabob4]

Re: Proper plumbing of bilge pump?

Kandil,
And where do you suggest the check valve be installed? If you install it just past the pump discharge, the hose will hold water. If you put it just before the t/hull, the backwash will be basically the same. So what's the point?

Moody, plumb the pump with a loop in the hose that starts upward from the t/hull, 8"-10" in diameter and secure it to an underside surface with a loom clamp. That's how virtually every builder in the world does it. A bilge pump is a centrifigal pump. When it shuts off, water will backflow into your bilge. I'd rather have water in my bilge than water in a hose that can raise it's evil stink!

 

[Bondo]

Re: Proper plumbing of bilge pump?

Ayuh,...

I Agree,... Put a Loop at the Top of the line....
The minuscule amount of back-wash is unimportant...

Check-valves will only Plug up with bilge debris...

 

[Utahboatnut]

Re: Proper plumbing of bilge pump?

I agree with Bondo the check valve will be more of a pita than it would ever be worth. They ALL backflow a tiny bit of water, if that is bothersome then you have a few options. Figure out where water is coming from and fix, have people doing watersports drip off a bit more before entering boat, or throw a absorbant pack down there and change when fully saturated.

 

[Nandy]

Re: Proper plumbing of bilge pump?

Most will use a wet/dry shop vac to dry the bilge. In my previous lake life where I was just a fisherman (read no teens coming in and out of the boat/water) I could dry my bilge with a towel even before pulling he plug... As much said, that little water amounts to nothing... Centrifugal pumps will leave water in the bilge anyway, they never pump it all... Do not use a check valve...

 

[Moody Blue]

Re: Proper plumbing of bilge pump?

I agree that the check valve is probably not the best approach for a number of reasons, the biggest being getting it clogged making the whole system useless.

What is the point of the loop off of the t/hull fitting? Is it to prevent any possible water intrusion from the outside?

 

[Bondo]

Re: Proper plumbing of bilge pump?

Is it to prevent any possible water intrusion from the outside?

Ayuh,... That's It...

 

[Mark42]

Re: Proper plumbing of bilge pump?

The instructions for a bilge pump I just installed said to avoid dips in the discharge hose that will hold water like a trap. That prevents water in the bilge from filling the pump, because the air in the pump can't escape with water in a trap. So the pump never pumps water, even though the float turns it on.

I would think that a check valve would do the same thing, especially if it has water pressing against it, keeping it closed.

Just install the hose like bondo said, with an upward loop to keep water out.