Holding tank won’t empty

Nov 10, 2009
21
Hunter 410 Rock Hall, MD
Not sure hearing is a definitive method compared with feeling it. If the vent doesn’t vent, you have the reason.
The vent screen on the aft holding tank was clogged or blocked by spiders and their webs. I disconnected the hose from the holding tank and connected a water hose to blow the obstruction off the screen. Worked like a charm. Pumps out just as expected now. As the tank nears empty, the sound of air being sucked into the tank is quite audible. This is on a 1998 Hunter 410.
 
Mar 26, 2011
3,968
Corsair F-24 MK I Deale, MD
Hmmmmmmmmmmmm ? ? ?

Not really. The pressure(s) in the loops are not additive. For every 24" of rise there's a 24" drop which hydraulically balances the previous rise.

No. This is a commonly held misconception. I've been in the tanker business, speced them out, and watched suction lines on spools fail time and again. I am a chemical engineer, and this is industry experience, not ideal theory speaking.

Hydraulic balancing ONLY happens when the loops are 100% full of liquid and if 100% of the air is purged. However, because of air leaks, because the line was empty to start, and because the pumping rate is not great enough to push all of the air out (liquid just dribbles over the high points at low startup rates), ideal assumptions are incorrect. If the flow were fast enough to purge all of the air (pumps are slow when priming) AND if there are zero air leaks at the coupling (there usually are not), the hydraulic balance assumption would be correct. But it doesn't work that way. You are making an ideal assumption that might be true at some stations but is not true at all stations.

Why do you think the instructions say to lay out the hose? Because it is important. Call Edison, the leading manufacturer of pump-out stations, why they printed that on there.