Jabsco 37010 Electric Head - Losing Prime

[Pilotpak]

I have a new Larson 310 with an electric Jabsco head.

The flush seems to be losing prime if not used for more than say 10 minutes. I have to hold the flush button down for 20 seconds to get raw water flowing. I'm guessing that the top of the head is about 2 feet above waterline. It's also very noisy.

Is this normal for a Jabsco ?

Shouldn't there be a backflow valve ?

Would it be much quieter if I removed the Flush impeller and installed a remote pump below water line (as in another post) ?

Thanks,

Wayne
2006 Larson 310 Cabrio

 

[Vic Willman]

Jabsco electric heads use a flexible rubber impeller to pump the raw water into the head. A flexible rubber impeller, by virtue of what it does, is just naturally noisy. Raritan uses 'em too, on all Crown Heads and also on older Crown Head II units. A rubber impeller has a maximum "lift" of 3 feet, so you're about halfway to the pump's limitation, with the top of the toilet being 2 feet above the waterline. Rubber impeller pumps don't hold their prime, but must re-prime themselves every time they are run - that's true with just about any pump that's being used for that purpose, not only with rubber impeller pumps.

If you were to remove the pump impeller, and use a diaphragm-type supply water pump, mounted closer to the through-hull fitting, it would operate a lot quieter. You'd simply join the wires from the two motors together, and run a hose from the output of the new pump to the elbow fitting at the rear of the toilet bowl, bypassing the toilet's existing intake pump altogether. But you must remove the impeller, you can't leave it in there - or the head will be even noisier! A FloJet or a Shurflow washdown pump should work well in that application. Diaphragm pumps run a lot quieter than impeller type pumps - just a little hum when they're running. Plus, most pumps that are used on marine toilets "push" the water a lot more efficiently than they "draw" it in, so mounting the pump closer to the through-hull fitting will improve the overall performance of the head.

On the discharge side, your Jabsco head has a centrifugal impeller that is very quiet in operation. Most people think that the noise associated with an electric marine toilet comes from the macerator and discharge pump - not true! It comes from the raw water pump.

 

[Pilotpak]

Thanks Vic,

Very Helpful Advice !

Wayne