So.....I installed a wash down pump and teed the pump input off the forward head sea cock. The installation went perfectly, (not a usual outcome), and we use the wash down system every time we haul anchor. It has really reduced the amount of stuff that wound up in the anchor locker. But....

Since installing the new wash down system the forward head isn't working. It won't pump water. I pump the Jabsco handle up and down to no avail, nothing but air.

The sea cock is below the water line. The tee is below the water line. The wash down pump draws water perfectly but the head pump doesn't.

The head input hose goes from the tee, up behind the head cabinetry and back down to the head. I really don't want to start cutting holes inside the cabinets to determine the hose path. If there's an anti-siphon valve hidden behind the cabinets I'll be really pixxed, who would do that? If it's just a loop that goes above the healed water line then it seems to me if the hose was full of water it could siphon.

I seemed to remember reading somewhere that you can push water through an anti-siphon valve but you can't pull water. That seems also to make sense. So I'm in a quandary.

Here's my lame duck thinking. When I turn on the wash down pump and pull the trigger on the hose nozzle, the pump pulls water from wherever it can get it. From the sea cock and maybe from water in the hose that loops up and down to the head, clearing out any water in the hose above the waterline. The head input hose would then essentially be empty except for the water from the tee to the waterline, right? So, the Jabsco pump and it's O-ring would have to create sufficient vacuum to draw the water up the hose, over the loop and then to the head. It just isn't happening.

Now, before the wash down pump, the head worked but I recall having to pump the handle several times to get the water flowing. I know I have the right hose because I connected the head input hose to the output of the wash down pump, ran the pump and the head pump worked perfectly, lots of water.

Ummm

Here's my brilliant idea. I'm going to insert a check valve in the head input hose as close to the tee as I can. This will serve to keep the wash down pump from sucking the head input hose dry. I'll try this and see what happens. If it works, I'll then be concerned about siphoning and will close the sea cock when sailing and when away from the boat. If it doesn't work, I'm open to your thoughts. Just like many of the V-bloggers I watch, they are always looking for comments on their projects. I know my reader base is incredibly small and my help expectations are quite low. But, one never knows, right?

I'll post the results of my check valve experiment.