Auto bilge pump problem.

[FrankJB]

I have a continuing problem with the automatic bilge pump on my LM 27. The LM 27 has a smallish sump in the bilge under the engine that probably holds about 5 litres of water.
Last winter I fitted a Sahara S1100 pump, which has an integral float switch. The problem is that because the sump is so small the column of water in the outlet hose runs back into the sump once the float switch tries to stop the pump restarting the pump starting a continuous loop!
A non-return valve seemed like a good idea so I fitted one as close to the pump as possible. This sort-of works but these valves do seem to leak especially when they suck up a bit of debris and they do restrict the free flow from the pump.
I can see that raising the pump in the within the sump would probably solve the problem but that would mean more water sloshing about in the bilge!
I’d be very grateful for any other ideas or solutions.

Thanks, Frank

 

[fisherman]

I fyou could make the outlet go up and then down, the down section would syphon the water from the up section. The final outlet could be close to the waterline, but the riser should keep it safe. If there were any chance of the outlet being submerged you could syphon water in and sink. Also a smaller outlet pipe would hold less water, possibly not enough to fire the pump again.

 

[FrankJB]

Fisherman,

That sounds exactly right! I just knew there must be a straightforward solution I hadn't thought of. Thank you very much.

Frank

 

[fisherman]

Sorry, realise the syphon idea won't work unless the outlet is lower than the pump, otherwise you will lengthen the pipe, it will hold more water, and it will all come back through the pump. The smaller pipe idea should work.

 

[pvb]

Use an electronic switch...

You could replace the float switch with an electronic switch which has an over-run time, designed to empty the bilge more effectively. Quick make one with a 20 second switch-off delay - see here for details.

 

[tugboat]

Your problem is one which vexes lots of people. Your pump is a high capacity model which is designed to shift a lot of water fast when you are in an emergency situation. At such a time you won't be concerned with a bit running back. My suggestion would be for you to fit an additional small manual or electric pump with which to transfer the last dregs to a suitable container. I used to have a boat with a shallow bilge and I used a brass garden sprayer (it looked a bit like a bicycle pump) and I doctored the nozzles so it pulled water in on the upstroke and pushed it out into a container on the downstroke. There are small boat pumps that would do the job for you or you could use one of those little brass pumps that are intended to sucking out engine oil and plumb it in permanently.