Non Return Valve after Bilge pump

[UFO]

The bathroom shower and sinks share the same through hull pipe as the manual bilge pump, so when you pump out the water from the bathrooms a percentage of it ends up in the bilge.


Is there any reason to NOT install a non return valve between where the bathroom pipe enters and the bilge pump?

[Nicholson58]

Many bilge pump makers say no to check valves. The consideration is that they can become blocked. I have only ever found them to simply fail to fully close.

All discharges should go to high points and over a loop with a vacuum (anti-siphon) breaker. The vents are high and as near to centerline as can be reasonably done. This is to locate the siphon breaker so that is always above the waterline. On our boat various discharge flows are then ducted to cockpit drains or deck scuppers. The drain after the high loop and vent is gravity down a large pipe. In this design, a check valve is not needed to keep miscellanies water from the bilge and the bilge line is alone. I have seen some boats where showers drain directly to the bilge. I don’t like that set up.

[Jon Hacking]

Originally Posted by Nicholson58

Many bilge pump makers say no to check valves. The consideration is that they can become blocked. I have only ever found them to simply fail to fully close.

All discharges should go to high points and over a loop with a vacuum (anti-siphon) breaker. The vents are high and as near to centerline as can be reasonably done. This is to locate the siphon breaker so that is always above the waterline. On our boat various discharge flows are then ducted to cockpit drains or deck scuppers. The drain after the high loop and vent is gravity down a large pipe. In this design, a check valve is not needed to keep miscellanies water from the bilge and the bilge line is alone...

Thanks for this, Nich. I had 4 really slow (pocketa-pocketa) heavy Jabsco bilge pumps, & replaced them with Rule Centrifugals, but those don't have valves, & the outlet is not very high above the waterline & it's shared by the manual bilge pump. So I put in check-valves, but I've had several problems with them, including them not closing properly.

A loop may well solve my problems, but while centrifugal pumps can pump a LOT of water quickly, they don't like much head. I think max head on my Rule 1300s is about 3'/1m. Do you have a solution here? TIA

[UFO]

Originally Posted by Nicholson58

Many bilge pump makers say no to check valves. The consideration is that they can become blocked. I have only ever found them to simply fail to fully close.

All discharges should go to high points and over a loop with a vacuum (anti-siphon) breaker. The vents are high and as near to centerline as can be reasonably done. This is to locate the siphon breaker so that is always above the waterline. On our boat various discharge flows are then ducted to cockpit drains or deck scuppers. The drain after the high loop and vent is gravity down a large pipe. In this design, a check valve is not needed to keep miscellanies water from the bilge and the bilge line is alone. I have seen some boats where showers drain directly to the bilge. I don’t like that set up.

Thanks for the Info I'll give the high loop a go.

[Nicholson58]

Check out the Whale electric bilge pumps. I have a few of these aboard for various tasks. Lots of lift head.

https://www.whalepumps.com/marine/pr...ic-bilge-pumps

My primary pump is Rule 3700. I am not wild about this thing. We have had a few failures over four years. Always at the worst time. I keep two pre-wired spares.

[deblen]

Centrifugal "rule" type pumps do not work well against the head caused by water held up the hose by a check valve. Manual "gusher" type diapragm pumps work a little better against a head-but still not well.
Suggest you install another above the waterline seacock & keep your device outlets(& inlets) separate.
There are many old threads on CF with horror stories due to multi devices on one thru hull.
Always put an anti syphon loop,or vent,in any overboard line. / Len

[Qayaq]

I find that centrfugal bilge pumps tend to airlock when fitted with a check valve, especially if you go from a dry bilge to flooded. So I drill a tiny hole in the outlet above the centrfuge height. This does spray a little jet of water out so try to angle it so jet stays away from wiring etc.The jet isnt great but its better than burning out tne bilge pump when the float switch sets it off and the pump just spins without pumping any water until you notice it..

[ggray]

Airlock can certainly be a problem.

My situation really demands a check valve, so occasionally causes airlock. I will relocate the check valve to high in the loop which should solve the problem