Check Valves and Pumps

[US1Fountain]

My shower sump, one of the small Attwood self contained units, is located at a distance enough that when it shuts off, the sump box fills 1/2 full just from the back flow. I installed a checkvalve right at the shower box discharge port to prevent this, but have since read several times to not use a check valve. I have no idea why.
Can someone explain why not?

Thanks

[sailvayu]

Check valves reduce the flow (by as much as 50%) and can clog. I am guessing you have heard not to use them for bilge pumps which is correct, but you should be fine using one on your shower sump. It could get clogged with hair but you can clean it if needed. Also sometimes adjusting the height of the float switch can help. I am using a 1/4 starboard shim in mine now which fixes the problem without reducing flow rate. If the valve works for you then no worries

Fair winds

[Jim Cate]

G'Day US1,
We've been using a check valve in our shower sump for about a year now (full time cruisers) and it has clogged once. Otherwise, has made life better, so I'd say go for it! If it doesn't work for you, it isn't hard to remove!

Cheers,

Jim and Ann s/v Insatiable II lying Broken Bay NSW Oz

[US1Fountain]

That's good to know. I couldn't figure out why not and never seen the reason explained. The bilge pump flow decrease does make sense now. We should be fine with ours then. We stay in our slip and just use the bath house at the marina for showering, so hair shouldn't be an issue.
Wayne, I'm not following the adjusting the float height. If I space it higher, I suspect the sump will maintain a higher water level since it turns on/off by the factory preset amount of water level change by the float switch. correct? BTW, this is a 1 peice pump/float unit.

Thanks

[sailvayu]

Ahh well if it is a built in pump float not much you can do. Most units have the float separate so if you raise it a bit the water running back into it has to be just a bit more to trigger it come back on. the thing is the pump tends to pull air at the end of the cycle so this little bit will sometimes make a difference. But your solution is fine and if it works stick with it.

Fair winds

[David M]

If you are concerned about your check valve causing you problems then put in a Y-valve on each side and create a bypass...just in case.

I would just put in the check valve and not worry about it. They are easy enough to replace plus its not in a mission critical place like a bilge pump outlet.