Head raw water pump primes slowly

[Navillus_83]

Hi All,

I have a Jabsco 37010 series electric toilet (single motor that spins a raw water impeller and macerator). Since purchasing the boat last summer, I’ve had a frustrating problem where I flush the toilet and the pump takes about 20 seconds to prime before raw water enters the bowl. Once it does, the flow rate seems adequate which tells me the impeller is likely not to blame. If I flush again within a few seconds, there is no issue, but if I wait just a few minutes between flushes, the problem occurs.

First of all, the head is slightly above the water line. I installed an in-line check valve close to the head (as opposed to close to the seacock) but this did not solve the problem. My working theory is that perhaps the check valve which sits roughly horizontally next to the toilet doesn’t have enough back pressure to close it (I believe it’s a joker valve style) allowing water to back flow. I’m thinking I need either a “flapper” style check valve, OR I need it put an upward loop in the intake hose between the check valve and the toilet so that gravity will cause enough water pressure to force the valve closed. I figured I’d get some opinions before I go out and buy anything else. Please let me know if you have any suggestions and thank you in advance!

Check valve I bought:
https://www.westmarine.com/whale-pum...e-1235530.html