"Air pocket" in raw water filter line

Stargazer3

Stargazer3

.
Feb 21, 2011
74
Hunter 410 Lorain
Hi, all! Whenever we come back from a day of sailing and turn on our air conditioning (or refrigerator) water pump - they run dry until we purge the line of inevitable "air pockets." We purge the air by unscrewing the filter bowls until water runs out - then screw them back in. Then each system runs fine.
We can't help thinking that there's GOT to be a better way! Let's hear from all you big boats out there and tell me what YOU do! Thanks! Capt Bill on STARGAZER
 
Don S/V ILLusion

Don S/V ILLusion

.
Sep 25, 2008
7,122
Alden 50 Sarasota, Florida
Even if the A/C was added as a factory option new boat purchase, the installation is done by whomever does the commissioning. Consequently, if the problem is a recurring one, the likely cause is either an air leak from a bad hose connection or the yard didn't locate the thruhull/pump/filter properly.

Can you elaborate on the configuration?
 
kloudie1

kloudie1

.
Nov 6, 2006
9,912
Hunter 34 Mandeville Louisiana
Lots of times the inlet might come clear of the water while heeled. Try closing that seacock when sailing and see if that solves the problem. Alternately, you can get the hose configured so that theere are no traps... that is, have the hose always rising from the seacock to the strainer then to the pump intake. No upward humps in the hose to trap air.. The pump intake on the pump case should be below the water level of the boat sitting level.
 
A

ALNims

.
Jul 31, 2014
208
Hunter 356 Huis Ten Bosch Marina, Sasebo, Japan
I have normally bled air from the discharge side of the seawater cooling pump. This ensures that both the pump suction line, filter suction line and filter bowl have no air trapped inside. If you just prime the filter bowls there will be air in the suction lines from the filter to the pump and also some air in the line to the filter bowl. If this doesn't help, then your next best option would be to close the inlet valve prior to leaving the dock. Another option would be to install a check valve in the suction line.
 
JamesG161

JamesG161

SBO Weather and Forecasting Forum Jim & John
Feb 14, 2014
7,495
Hunter 430 Waveland, MS
Most sea water pumps inlets should have been installed BELOW the actual water line (AWL) of your boat and all those inlet lines too.

If opening the inlet stainers allows water to flow into your boat, then they are below the AWL.

Trace the line from those strainers to they pump inlets (suction). If those lines are alway below the AWL, then you should have a flooded pump.

Last...

If all of the above stuff is below the AWL, then your pumps are NOT free to flow, as designed. I assume those devices are discharge ABOVE the AWL or out into the air.

So...

If your equipment ALWAYS did this, then you have a "seal trap". What is that? Look under your kitchen sink that has a "U Trap, Seal Trap, P Trap". That TRAP prevents sewer gas from escaping into your house. Just like the Air TRAPED in your boat systems.

My Guess...

Since you have 2 systems not working well my guess this is NOT true...
Then each system runs fine
Click to expand
but they are BARELY working.

My AC was cutting on and off. I was about to call a Tech. Neighbor boat owner told me, "I can fix it!" and he did. There was water discharging, too. I thought is was FINE.

He closed the sea cock, took off the discharge hose, brought a "As Seen on TV" flex hose with a shut off valve and a tapered tip. He jammed that tip into the hose, turned on Dock water pressure and about a ton of algae and crap blew out the over board discharge. We purged it for about 3 minutes or until it was clear water. He reassembled the system, opened the sea cock, and now a major change it the flow of water. My AC got cooler and stopped the cycling since it was at high temperature cut off.

I do this now annually.
Take Care
Jim...
 
You must log in or register to reply here.

Top Bottom