2021 Tab 320 pump runs, won't suck thru sanitize port

Captenaj

I have a 2021 320S Boondock. For a while I was having trouble where the pump would not shut off despite all faucets being closed. I read suggestion that said to fill the fresh water tank - that stopped my pump from running. But recently when I connect a hose to the Nautilus winterize/sanitize port and turn the pump on, green knob pointed left and blue knob pointed down, liquid is not getting sucked into the system. I hear the pump running but nothing is getting sucked up. When I put the Nautilus in "dry camp" position, water comes through the faucets fine. What could be going on? Thanks.

bergger

Your pump is loosing its prime in sanitize mode.  This is very common.  Mine lost it a few times today when I was wintering.  You just need to prime it again.  The easiest way I found was to hold the short hose above the hose input and pour water into it.  Then turn on the pump.  You should see some water go down the hose but turn off the pump before it sucks it all out.  Then pour in some more.  Repeat as necessary. Some times I will actually pour the water in and then as the pump runs blow the water down the hose.  Once it is primed it also helps to keep you container of water or antifreeze above the level of the input.  

Maxcamp

We consistently lose pump prime when moving.  Stationary is fine. Less frequent with full tank, more frequent with less full fresh water tank.  So tank airspace is getting into inlet valve. 

 A short hose and water bottle or large cup filled from CW drain allows us to reprime using Sanitize pump suction mode.  Then immediately shift to boondock mode and cycle pump till pressurized.  I keep hose and plastic bottle in the water panel.

BridgerSunset

I want to believe that the "sanitize / winterize " port is only meant to suck fluid out of a jug or bucket, via a very short suction hose.  Are you connecting to it with a long hose? 

If so, your problem may be  attributed to the fact that the pump only has so much "suction lift" capability,  and a long hose causes too much friction loss to keep the pump charged sufficiently.  Yeah, use a sort suction hose & follow what the guys above are saying.

Captenaj

Thank you for your help! I connected a short hose, slowly filled it from a cup, and once I had done that a few times it worked fine. I'm greatly relieved it's not something bigger.

Mobean

We had the same issue after turning on the Alde with a low fresh water tank.  Sharon_is_SAM previously suggested tipping the TAB with the hitch jack so the front is higher than the back.  Worked well and sure beat hitching the TAB back up to go fill the tank. Apparently the tipping moves air bubbles towards the faucet and allows the pump to self-prime again.  The RV education continues...

Sharon_is_SAM

@Mobean  - on the 2021s, the outlet to the pump is in the rear of the fresh water tank.  By raising the Jack, more water is available to the pump, so less sucking of air and the prime is maintained.  

Captenaj

This is very helpful. Thank you to all!