New Shower Sump - Air Lock?

firecadet613

Well-Known Member
May 10, 2007
5,253
Indiana
Boat Info
SOLD - 2007 Four Winns V358
Engines
Twin VP 5.7GXi V-Drive / ZF63s
Just put a new shower sump on the boat - replaced the original since I moved the galley sink to drain overboard.

Issue I'm having is it will pump the water just fine, but the next time it fills up it may pump it just fine or the pump will turn on and pump nothing. I can push the float down by hand to turn it off and when I let go about half the time the pump will come back on and pump the water, other half the time it'll come on and run but not pump water.

Seems like the pump is getting air locked which is hard to believe, given that there is always water left in the sump when it's done pumping. Has anyone encountered this before or come up with a remedy?

Here is the sump I installed, a run of the mill Rule Shower Sump...
https://www.defender.com/product3.jsp?path=-1|51|2234226|2234234&id=4563636
 
Something is not properly sealed in the pump and losing prime. Just replace it. The same pump box I installed last year. Why move galley off the pump?

MM
 
Something is not properly sealed in the pump and losing prime. Just replace it. The same pump box I installed last year. Why move galley off the pump?

MM

Just picked up a backup pump on Amazon so I'll swap the pump out tomorrow. Never been a fan of food bits going to the shower sump then overboard - first thing I did on my 318.
 
If you have a check valve you can get an air lock. You can drill a small hole on the pump discharge inside the box. I had same problem
 
If you have a check valve you can get an air lock. You can drill a small hole on the pump discharge inside the box. I had same problem

It does have a check valve...needs it as the hose holds a lot!

If I'm understanding correctly....just drill a small hole on the pump where it discharges, before it exits the box, on the pump itself?
 
yep. 1/8” would be fine.
what happens is when the pump empties the box, air gets in the pump. as water comes in, the air is trapped between the pump and check valve. when pump turns on it can’t pump air, so it just runs but nothing happens. the hole allows the air to escape as the pump fills up.

point the hole down so it doesn’t squirt you in the face as you’re watching to see if it works.
 
yep. 1/8” would be fine.
what happens is when the pump empties the box, air gets in the pump. as water comes in, the air is trapped between the pump and check valve. when pump turns on it can’t pump air, so it just runs but nothing happens. the hole allows the air to escape as the pump fills up.

point the hole down so it doesn’t squirt you in the face as you’re watching to see if it works.

Makes perfect sense. Thanks!
 
I put a call into Rule yesterday and they just called me back. They've identified an issue causing the newer boxes to air lock and have redesigned it.

New box is on the way and I can keep the old box for spare parts. Now that's service!
 
I put a call into Rule yesterday and they just called me back. They've identified an issue causing the newer boxes to air lock and have redesigned it.

New box is on the way and I can keep the old box for spare parts. Now that's service!

How did the new box work for you? I'm having the same issue with the Rule box in the boat I recently purchased. It was installed in 2019.

Has anyone else tried drilling the hole?
 
How did the new box work for you? I'm having the same issue with the Rule box in the boat I recently purchased. It was installed in 2019.

Has anyone else tried drilling the hole?

I am pretty sure my Shower Sump Pump box gets some sort of air lock also. Didn't know if it was related to the float or the pump.
 
What type of box do you have? If it air locks, it will not pump at all, just run and run. Air lock has no affect on the float switch.
 
Well the float can keep the pump running in the same manner as an air lock could keep it running.

I might try drilling the small hole. Do you mean in the exit hose right after the pump but still inside the sump box?
 
No issues with the new box. It raised the float up about an inch.
 
How did the new box work for you? I'm having the same issue with the Rule box in the boat I recently purchased. It was installed in 2019.

Has anyone else tried drilling the hole?

The hole will work, but I sealed it up and now that's my spare pump since I installed the new box.
 
Well the float can keep the pump running in the same manner as an air lock could keep it running.

Not exactly. A faulty float could keep the pump running longer than needed (ie. after the box is dry) or not turn it on at all.

Air lock is when the pump is running but nothing is being discharged due to an air bubble under the impeller, usually causing the box to remain full or overflow.
 

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