Bilge Pump check valve issue

[Briankinley2004]

My a/c condensate sump and shower sump did not have check valves in the bilge pump discharges when I purchased my boat. Last year I installed one in my a/c sump because I was tired of water flowing back through the pump and standing pretty deep in the sump. After installing it sometimes the pump would run but not discharge anything. Being easy to access I would simply lower the float switch to turn the pump off then let it float again. It would then begin to bump and shut off normally. It was almost if it was airlocked or something. As time progressed the problem has gotten better and actually I can't remember the last time I had to manually shut this one off. It gets a fair amount of water in it as I hose the engine room floor from time to time

A few weeks ago I did the shower sump as I was tired of the water standing in there and going sour. I could pump it out with the manual switch but it would back flow into the sump. So did same thing, installed a check valve. Well it is doing the same thing as the other sump but this one involves picking up a floor hatch and going head first into the bilge. Robert has a good picture showing this. I am thinking of taking the check valve out and just dumping bleach in there when I leave the boat but wanted to see if anyone here has suggestions on how to fix this. I guess it is either not able to produce enough head to open the switch or something however I don't understand why it works once I shut the pump off then turn back on. Any ideas?

 

[osprey]

IMHO, centrifugal Bilge pumps are not pressure pumps. if the outlet hose is full of water, the water pressure sitting on the check valve is too much for the pump to push against so the pump will cavitate. There are solutions, different pumps and set ups. Good luck

 

[Briankinley2004]

IMHO, centrifugal Bilge pumps are not pressure pumps. if the outlet hose is full of water, the water pressure sitting on the check valve is too much for the pump to push against so the pump will cavitate. There are solutions, different pumps and set ups. Good luck

If this is the case why does it start working when I re-start pump by holding float down. Your analysis makes a lot of sense to me but I would think it wouldn't work when I re-start pump as hose is still full of water.

 

[racclarkson@gmail.com]

My solution is place check valve very close to bilge pump. Then add fall to drain hose just as soon as you got it high enough to do so. Water over the hump flows out making it easier on the pump. When in one application that wouldn’t work, I added a second check valve several feet downstream.

 

[Pascal]

Check valves on bulge and sump pumps should be a last resort. It s not a matter of if they will stick or causing the pump to air lock but when. Every single one I ve seen has cause a problem. The only one to consider if you really have to are the heavy duty bronze one but even then will cause problem

The only time I use them is if i have a very small sump or bilge and a long hose run causing the pump to short cycle. When possible getting the discharge hose to a high point close to the pump and then sloping down to the TH helpsn

There always will be some water in the sump. With a cover on odors should not be a problem.

 

[racclarkson@gmail.com]

Actually, I've had better luck with the inexpensive flapper type valves. There is no spring pressure added to water weight to overcome.

https://www.seamar.com/item/BOS074-8/INLINE-CHECK-VALVE-1-HOSE/

If you keep a clean bilge there is less chance to clog. If you use the flapper valve there is minimal clogging potential viz the more expensive spring loaded models, regardless of construction material.

The residual shower sump water is a valid issue. Nothing easy to be done but cover and/or add a bit of bleach or drop-in bleach tab.

However, I do agree it's unwise to depend on a check valve to prevent flooding. Always get the discharge well above the waterline and then give it fall to prevent reverse siphoning.

 

[Fanfare]

There was no room for a shower sump on the 50MY due to hull shape so the after shower was drained by Hatteras with a diaphragm pump, a PAR Sea Gulp Jr. This always worked well. The bow shower had the usual centrifugal submersible bilge pump in a large sump but this had two problems: smelly residual water and loss of efficiency due to accumulation of tangles of hair around the impeller. I finally replaced this pump with another PAR diaphragm bilge pump mounted outside the sump. This has worked well even though we don't use this shower much. It is not an enclosed shower and its shower curtain gets the head's deck wet. The diaphragm pump does not seem to have the back-flow problem of the centrifugal.

Hatteras ran the aft shower discharge hose all the way forward to the generator compartment where it discharged above the water line below the flare of the bow. When I re-engined some 25 years ago this line was accidentally cut so I moved the PAR pump to the stbd. engine room where it might be more accessible. Then I learned why Hatteras put it forward--it makes loud burbling noises which were formerly redirected by the flare below the bow. I have not bothered to fix it. At least it lets me know if our guests are using too much water!

After about 45 years I did have to extract a large hair ball from the drain hose so a strainer just before the pump inlet might be a good addition.

 

[Briankinley2004]

For clarification the valve I used is what Robert linked too or similar. A flapper valve not spring loaded check valve. All three showers drain to one sump so I guess I would need a visual on how to put a diaphragm pump to the sump. I do have the valve right at the outlet of the bilge pump. It is a very tight fit to get the valve in there and make the turn up and out of the sump. Im going to give it some time to see if it gets better like the one in the engine room and if it doesn't will remove and just pour bleach in there.

Also all my other bilge pumps except the aft one have check valves on them and have no issues. I did not install them but they are good at preventing residual water. I don't think they were installed to prevent flooding as the discharge is well above the water line and the valves are right at the pump. The engine room discharge hoses run quite a way from the pump to where they exit.