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 Backup sump - check valve location
Author: Gadgetdude (IL)

I'm hoping I can get some opinions on a backup sump issue I've been having.

I have a StormPro battery backup system (1 battery w/ inverter) with two 1/2HP pumps setup as a primary on AC and a secondary connected to the inverter - both pumps have clear check/flap valves installed. I've been very happy with the solution for the last 5+ years but have a problem when testing the failover that has been getting worse over time.

The primary pumps like a beast and never has any trouble starting up or pumping strong (Chicago suburbs so it pumps a lot). The issue happens when I test the secondary pump by unplugging both the primary and the battery to kick into full battery failover.

The secondary pump kicks turns right on as it should but I have a problem with air that is trapped between the pump and the check valve. Both pumps have a relief holes drilled pointed down just above the water line but on the secondary pump it isn't enough. What would happen after months of not running between tests the secondary pump comes on and I can see some water and bubbles coming out of the relief hole and after a few minutes it would clear enough air to build enough pressure to push past the check valve and shoot the remaining air up and out along with the first cycle of water. Once it cycled once it will continue to cycle/pump for hours like a champ - it is just the issue with the trapped air on the first cycle. Over the years whenever I tested it seemed like it would take longer for that first initial air clearing so I called the installer out and we moved the relief hole up a bit higher and that seemed to help but now I'm back to it taking longer to clear the air on the first test cycle.

I am thinking the issue is the location of the check valve on the secondary pump. On the primary the check valve is about 3ft above the top of the pump and it has no problems ever. For some reason the check valve on the secondary is higher and a bit over 4ft above the top of the pump and about 3ft above the relief hole. When the secondary is trying to clear the air on the first cycle I have confirmed that the trapped air is the problem by slightly loosening the connector under the check valve which releases a bunch of pressurized air and once the air is gone we're off an pumping (literally 1-2 seconds max and I can do it carefully/fast enough not to soak myself!)

What I am thinking is that there is just too much air between the relief hole and the check valve for the pump to overcome once it has sat idle for a few months and if I lowered the check valve to about the same height as where it is on the primary or even a bit lower (maybe 18 inches above the relief hole instead of 36) that might solve my problem. I know the danger if the check valve is too low so that the pumps can't overcome the weight of the water above the check valve but given how strong these pump seem I think I'll be ok.

Your thoughts - is my reasoning on track or am I missing something?

Edited 1 times.

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