Rerouting a bilge pump discharge

[openseas]

Hi all,
The discharge of my bilge pump opens below the water on the port side of the boat. I want to change it to the stern of the boat. What kind of valve I should put to prevent a reverse flow of water, and where should I put it ( how close to the bilge pump verses to the discharge), also what kind of hose is considered a heavy duty one for this situation?
Thanks,

Andrew

[Terra Nova]

Never place a valve in a bilge pump line.

[roverhi]

The bilge pump people make a plastic check valve to stop flow back in the line. I put it next to the pump so all the water in the line doesn't run back to the bilge. Have a loop with an anti syphon valve so the pump outlet won't reverse flow into the bilge if it's under water. The water running back to the bilge can be an issue if your bilge sump is small. The water draining out of the hose can trigger the bilge pump float switch resulting in constant cycling.

A swing check valve would be another possible back flow preventer. You can buy them at any big box building supply store. I don't use them in the bilge pump, only in the boat's fresh water system, because don't know if they are brass or bronze from those sources. Would assume if you can find them at a marine store they would be bronze.

[Cheechako]

If installing the swing check, install it horizontal. Frankly though, I prefer a big loop of hose in the stern prior to exiting and no valve.

[openseas]

Originally Posted by roverhi

The bilge pump people make a plastic check valve to stop flow back in the line. I put it next to the pump so all the water in the line doesn't run back to the bilge. Have a loop with an anti syphon valve so the pump outlet won't reverse flow into the bilge if it's under water. The water running back to the bilge can be an issue if your bilge sump is small. The water draining out of the hose can trigger the bilge pump float switch resulting in constant cycling.

A swing check valve would be another possible back flow preventer. You can buy them at any big box building supply store. I don't use them in the bilge pump, only in the boat's fresh water system, because don't know if they are brass or bronze from those sources. Would assume if you can find them at a marine store they would be bronze.

Hi,
So do I need a check valve and anti syhon valve at the same time?
Andy

[Cheechako]

Originally Posted by openseas

Hi,
So do I need a check valve and anti syhon valve at the same time?
Andy

No, assuming you put anti siphon valve in a loop above the waterline.

[roverhi]

What Cheechako said. The check valve will just keep whatever is in the hose from backflowing. That was an issue on my last boat. The anti syphon valve should stop any flow of seawater back into the boat.

[Terra Nova]

Besides being a permanent restriction, which reduces flow and promotes clogging, check valves can fail to open.

If you improperly install the wrong type of bilge pump or float switch, or plumb it incorrectly, enough water can back-flow to cause cycling of the pump. This often happens with centrifugal pumps when the float switch is set too low, and there is a long discharge run.

Alternatively there are switches that continue to run the pump for a few seconds after a normal switch would have shut down. A diaphragm pump can also be used to dry the bilge.