Bilge pump drain back

[Kamahele]

I have a shower drain sump that has a float switch and an 1100 gph impeller bilge pump. The sump is about 2-3 ft below the in-hull outlet fitting and there's about a 7-8 ft run of 1-1/8" hose between the pump and the in-hull fitting. My question is whether I could reduce backflow to the pump after the float switch cuts off by looping the hose up above the hull outlet about half-way through the hose run. That way, I would think, some of the flow would go out the in-hull fitting, and the rest flow back through the pump into the sump, thereby reducing the amount of backflow. Or would a siphon effect happen and all of the flow go back into the pump anyway? Any ideas on this appreciated.

 

[beason]

Re: Bilge pump drain back

my bilge pump has a loop just before the hull fitting. its about a 4 or 5ft run.

 

[alldodge]

Re: Bilge pump drain back

I have a shower drain sump that has a float switch and an 1100 gph impeller bilge pump. The sump is about 2-3 ft below the in-hull outlet fitting and there's about a 7-8 ft run of 1-1/8" hose between the pump and the in-hull fitting. My question is. That way, I would think, some of the flow would go out the in-hull fitting, and the rest flow back through the pump into the sump, thereby reducing the amount of backflow. Or would a siphon effect happen and all of the flow go back into the pump anyway? Any ideas on this appreciated. whether I could reduce backflow to the pump after the float switch cuts off by looping the hose up above the hull outlet about half-way through the hose run

I see no reason it would not work. The output would be reduced by the distance the water has to be lifted, but I don't see that as an issue with a shower bilge pump. Don't see an issue with a siphon either. Most of the shower bilge duck bills don't last long before they start to leak

 

[bruceb58]

Re: Bilge pump drain back

Would a check valve help? Not sure if they ever put those on boats. We have a sump pump under our vacation house and we pretty much have to have it or the pump just cycles on and off.

 

[smokeonthewater]

Re: Bilge pump drain back

the loop would ONLY work if you installed a siphon break

you COULD drop to 3/4" hose which would help and still carry PLENTY of water for a normal low volume boat shower

As mentioned above a check valve could be used too

 

[alldodge]

Re: Bilge pump drain back

Would a check valve help? Not sure if they ever put those on boats. We have a sump pump under our vacation house and we pretty much have to have it or the pump just cycles on and off.

The check valve so to speak is the duck valve at the exit of the pump output on the pump on the shower bilge. They don't last long and wear out, just a flap of rubber

the loop would ONLY work if you installed a siphon break

you COULD drop to 3/4" hose which would help and still carry PLENTY of water for a normal low volume boat shower

As mentioned above a check valve could be used too

If the siphon happened going from the bilge to overboard, this would be good. Now the only way the siphon would work in the other direction would be if the output was below the water line, which the OP said it was not, and shouldn't be.

 

[UncleWillie]

Re: Bilge pump drain back

I don't think the concern is a continuous siphon of water into the boat and sinking it.

Consider that the shower hose goes up to a high point and then runs a short distance to the hull through.
When the pump shuts off you would hope that the water after the high point would run overboard and the water before the high point would flow back to the shower pump a few feet below.
In reality almost all the water up to the hull through gets sucked back to the pump before it has a chance to drain out.
A siphon break at the high point would make it work, but that is a lot of extra complications to save a pint of return flow.
The check valve, even a leaky one, would give enough time for the end of the hose to drain overboard.
+1 on the smaller diameter hose.

Is it really a big deal. When the pump shuts off, there is still an inch or more of water in the shower sump.

 

[smokeonthewater]

Re: Bilge pump drain back

yep the point of the siphon break is to 'split' the water in the hose... after drains overboard and before returns

fwiw MY shower uses a diaphragm pump on 3/4" hosenear the thru hull with no sump... simply turn on and take shower.... I don't get any drain back issues at all

 

[Grandad]

Re: Bilge pump drain back

A siphon break will help, but I'd also suggest that the high point break be placed as close as possible to the shower rather than near the through hull. The difference in the height of the water at each side of the high point determines which direction it will flow, but the volume depends upon the length of the tube. Keeping the high point siphon break near the shower will minimize the volume that will flow back into the shower. - Grandad
Universal Washing Machine Siphon Break Replacement Washer Syphon Breaker LP1586

 

[alldodge]

Re: Bilge pump drain back

Get your point on the siphon break. The flapper valve that comes with the shower bilge is just a piece of rubber that a hole has been cut in it and hangs from the top. If the hose goes up high first and does siphon back, will be the same as if it was low and it ran back due to gravity. I would guess the high route would help and may not have all of the water run back, mainly because the flapper valve will slow it down.

Other option is a PVC swing check valve. The swing valve is the same as the flapper but built better to hold up longer. Don't know how much if any back pressure would be found. The ones I'm thinking about do not use springs

Clear PVC Swing Check Valves

 

[JASinIL2006]

Re: Bilge pump drain back

I could see a check valve on a shower drain, but someone above mentioned using a check valve on the bilge pump. Is it common practice to put a check valve on the bilge pump outlet?

I'm asking because I've seen enough check valves fail that I'm not sure I'd want one on a bilge pump, especially on a moored boat. The most recent failure was on a check valve on a sump pump line in my parents' basement. The flapper inside the valve broke loose and effectively plugged the outlet hole every time the pump came on. The basement flooded.

Don't mean to hijack, but a post above got me wondering about it...

Jim

 

[Kamahele]

Re: Bilge pump drain back

I see no reason it would not work. The output would be reduced by the distance the water has to be lifted, but I don't see that as an issue with a shower bilge pump. Don't see an issue with a siphon either. Most of the shower bilge duck bills don't last long before they start to leak

What is a "duck bill" in this context?

 

[alldodge]

Re: Bilge pump drain back

What is a "duck bill" in this context?

I am making things a bit messier. A duck bill is most often used on pluming areas like the pump toilet flushing area, and they require a bit more pressure to operate. It opens when water is pushed through it and closes off.



The swing valve or flapper valves work like through hull exhaust flappers. Water can go out easy but valve closes when water tries to come back. The ones in a shore bilge are pretty cheap flappers and many use the term duck bills and I should not have used that term.

 

[Kamahele]

Re: Bilge pump drain back

Thanks everyone. Good suggestions to mull over.
One time I tried using a 1/2" check valve (spring type) with a 500gph impeller bilge pump, but it didn't generate enough pressure to open the valve (and yes i did have the valve installed the right way). So, i have hesitated to use a check valve as part of the solution, but I'll look into the flapper type. I understand they need less pressure to open.

 

[Kamahele]

Re: Bilge pump drain back

Thanks for the clarification. Any suggestion where to find a flapper valve that would work in this installation?

 

[alldodge]

Re: Bilge pump drain back

Thanks for the clarification. Any suggestion where to find a flapper valve that would work in this installation?

One place is the link I left in post #10, has all kinds of sizes. Find one that fits your hose
There are probably other places just google

 

[UncleWillie]

Re: Bilge pump drain back

What is a "duck bill" in this context?

A very simple valve with essentially no moving parts.
Usually molded of rubber with a slit cut in one end and looks like a Duck's Bill.

It works like your lips. Close your mouth loosely and you can blow out but not suck in.

Duck Bill Valve.

 

[Kamahele]

Re: Bilge pump drain back

One place is the link I left in post #10, has all kinds of sizes. Find one that fits your hose
There are probably other places just google

Thanks, I missed the link in your #10 post. Good price on a 1" flapper valve from these guys. Problem is they want twice that amount to ship it here! I'll keep looking. Maybe at a local pool and spa place here.

 

[Kamahele]

Re: Bilge pump drain back

A very simple valve with essentially no moving parts.
Usually molded of rubber with a slit cut in one end and looks like a Duck's Bill.

It works like your lips. Close your mouth loosely and you can blow out but not suck in.

Duck Bill Valve.

I know these things as "joker" valves.

 

[Kamahele]

Re: Bilge pump drain back

fwiw MY shower uses a diaphragm pump on 3/4" hosenear the thru hull with no sump... simply turn on and take shower.... I don't get any drain back issues at all

Doesn't the pump get clogged with soap scum, etc? Do you have a strainer attached before the pump?