My Shurflo ProBlaster Washdown Pump has always worked great. This year I changed my Head and now it doesn't work so hot ... it's sucking air. The inlet for the Washdown and Head are the same.

The previous plumbing was as follows > from the thru-hull / Seacock 3/4" intake, there was a T shortly thereafter. One run went straight to the Washdown Pump Inlet, and from there to the deck fitting where I attach my hose. The other run from the T went to the Inlet side of the manual pump housing on a Raritan PHII, from there the 3/4" line exited the back of the pump and went to a Vented Loop well above above waterline, then back to the rear of the Head bowl to fill the bowl & flush.

This year I installed a Raritan Marine Elegance Electric Head. Now the plumbing goes as follows > from the thru-hull / Seacock 3/4" intake, a 3/4" line goes to a Groco WSB-750 Strainer, from there to a T. One run (via a ball valve) to the Inlet of the ProBlaster Washdown Pump and from there to the deck fitting where I attach my hose like before. The other run goes from the T to the Inlet side of the Remote Pump for the Marine Elegance, then to the Vented Loop (which has not changed location) and from there to the Head.

If I take the 3/4" line that goes from the ball valve (after the T) to the Washdown pump off just after the ball valve, stick that into a bucket of water, and turn on the Washdown, it works great, plenty of power, no sucking air.

I'm wondering if the Washdown is now somehow sucking water back out the Remote Pump (and not from the Sea Cock / thru hull via the Strainer), and out of the Vented Loop, and therefore sucking air from the duckbill of the Vented Loop as the flow is now going backwards ? If that's the case, I'm wondering why water was able to be sucked through the new Marine Elegance Remote Pump, but not the old manual pump of the PHII ? I can't imagine the introduction of the Groco Strainer has anything to do with this problem. The boat is 2000 miles away ... what I have not yet tried is to cap off the 3/4" hose before it goes into the Remote Pump and see if the problem goes away.

I did check all hose connections and all are tight.

Thanks, cheers, John