Pressure water pump runs on for no apparent reason

[Skipper]

-RESOLVED-

Of all the systems on this boat, the domestic water system requires the most attention. I've replace the water heater with HTP SuperStor, replaced the diaphragm and couplings\check valve on the Jabsco 36950-2 pump, cleaned the water tanks, purged the accumulator including again today, rebuilt the manual hand pump, and kept the system winterized\drained in the off season.

Now it's acting up again. Started after spring commissioning. The current problem being addressed is that the pump keeps loosing its suction, and starts to run on when the galley sink faucet is opened(The tank is kept full). I then have to open the head sink faucet with the pump on to get it to suck water again. it only occurs if the system has sat unused for a bit. If i'm using it after getting suction, all is good for the time being.

The odd thing is that there are no leaks anywhere; the system stays pressurized for hours, and the pump doesn't trigger when the faucets are closed. The pump only runs on when I open the faucet after awhile, and the pressure switch trips. The system then looses its initial pressure into the sink while the pump spins in vain with no load. Very strange.

I had posted another topic re fizzy water on the hot side. It is likely the chlorine bleach used to shock the lines that is reacting. The fizz is still there, after running much water through the heater. Although, it seems to be dimishing. I thought that maybe the fizz-gas in the heater was putting air in the system, but the same symptom occurs when I only open the cold side.

I've exhausted my ideas. Any help would be greatly appreciated.

 

[kloudie1]

Sounds like an air leak on the suction side. One of the fittings or maybe a gasket in a pre-pump strainer, or a valve packing .. I have a tank selector valve which had a leaking o-ring; it showed the same symptoms . if you have two tanks ad one is empty, suspect the isolation valve. If only one tank, suspect all fittings between the tank and the pump.. especially any that may have been disturbed while doing the pump work. Suction side leaks can allow air in without water leaking out.

 

[centerline]

it sounds like the valves and impeller in the pump are good, but there is an air leak between the tank and the pump.... it may not leak water, but can suck air when the pump comes on, which would explain everything.

when the pump is primed and has pressure built in the accumulator, it is all good and normal, but as it sets with the accumulator charged and awaiting use, the small air leak on the suction side of the pump will allow the prime to be lost back into the tank.
then as soon as the accumulator pressure drops just a little which allows the pump to come on, the impeller cannot pick up a prime without somewhere for the air to escape... and the pump WILL NOT pump the air and compress it into the accumulator, so the pump runs on trying to find its water.

when you open the faucet LONG ENOUGH so enough volume escapes and the pump can push the air thru, it can then get the water and recharge the system in its normal way.... until the prime drains back into the tank..

re-plumb the line from the tank to the pump and make sure all connections and fittings are sealed completely

 

[sd1953]

Sounds like a small leak in the line going to the galley sink that is NOT leaking water out, but allowing air in and then air binding the pump. How close is the pump and tee fitting that goes off to the sinks? You might profit from wrapping the fittings on the galley sink line with saran wrap and see if the problem persists. If not, then one of those fittings is allowing air to leak in (the fitting is above the pump? and the pump above the tank?) breaking the water seal and allowing water to run back down into the tank. If the pump and fitting are BELOW the tank level, then this cannot be the problem. And I have no help for you.
I have no help for you on the fizzy hot water... sorry.

 

[Skipper]

Sounds like an air leak on the suction side....Suction side leaks can allow air in without water leaking out.

OMG that was it! --I'm on the boat so your info went into immediate service.

I had replaced the plastic inlet-coupling (I broke it) on the back of the pump at commissioning. I had then tightened the hose clamp with a stubby rachet-screwdriver (my favorite tool), and I guess it wasn't tight enough. I used a bigger screwdriver now and it took another quarter turn. Now the flow is perfect. Jeez so simple. I didn't know the system could suck air and not leak water, so didn't think to check the clamps. A new plumbing piece of knowledge now in my arsenal.

Thank you

 

[Ralph Johnstone]

purged the accumulator including again today,

Not clear on why you would want to purge the accumulator.

You want the accumulator pumped to approximately 50% of your average operating water pressure and measured with zero pressure in the delivery piping. If it's a Jabsco, it has a rubber diaphragm in it and usually lasts for several years on a pumped air charge.

The leaking inlet was my guess as well ................. glad it was a simple fix.

 

[Skipper]

Not clear on why you would want to purge the accumulator.

Attached - page 2, item 5.

I too didn't think it was the accumulator causing these symptoms, but I was trying everything.

 

[Ralph Johnstone]

Attached - page 2, item 5.

I too didn't think it was the accumulator causing these symptoms, but I was trying everything.

Wow ............ that model looks like a blast from the past, a real mouldy oldy. It definitely would need periodic draining and refilling with air. The problem with that older model is that there's no diaphragm between the air and the water and the water will slowly dissolve the air. Hence the air disappears.

But you were right in saying that the accumulator was not connected to the suction problem.

 

[Bill Roosa]

the pump valves are leaking internally and just need to be cleaned.

 

[kloudie1]

You are welcome, Skipper!.. Had same symptoms on my boat and a couple of buddy's boats.. found air sucking in at a partially tightened suction fitting on two and a leaking valve packing on mine. Centerline probably has seen that one too. Good that it was a quick and easy !

 

[Skipper]

Wow ............ that model looks like a blast from the past, a real mouldy oldy. .

Yep she's 30 this year. No mold though. The accumulator is original.

 

[Skipper]

it sounds like the valves and impeller in the pump are good, but there is an air leak between the tank and the pump.... it may not leak water, but can suck air when the pump comes on, which would explain everything. when the pump is primed and has pressure built in the accumulator, it is all good and normal, but as it sets with the accumulator charged and awaiting use, the small air leak on the suction side of the pump will allow the prime to be lost back into the tank. then as soon as the accumulator pressure drops just a little which allows the pump to come on, the impeller cannot pick up a prime without somewhere for the air to escape... and the pump WILL NOT pump the air and compress it into the accumulator, so the pump runs on trying to find its water. when you open the faucet LONG ENOUGH so enough volume escapes and the pump can push the air thru, it can then get the water and recharge the system in its normal way.... until the prime drains back into the tank.. re-plumb the line from the tank to the pump and make sure all connections and fittings are sealed completely

Your description turned out to be exactly right in every detail. Thanks for the input.

 

[Stu Jackson]

And once you fix this one, you might want to replace all the outlet hoses, like I just did! That'll be your next leak! Pretty much the only stuff left you ahve't done yet!

 

[Barnacle Bill]

And, your original comment saying ".....for no apparent reason" was inaccurate. There always is an apparent reason.

 

[Skipper]

And, your original comment saying ".....for no apparent reason" was inaccurate. There always is an apparent reason.

ap·par·ent /əˈparənt,əˈpe(ə)r-/

adjective

1. clearly visible or understood; obvious.

 

[Ralph Johnstone]

Not Finished by a Long Shot .................

you might want to replace all the outlet hoses, Pretty much the only stuff left you ahve't done yet!

........................ then there'll be the faucets 'cause they're startin' to show their age :neutral:, and the sink could also use an upgrade to match the new faucets :cry:, and the drain hose from the new sink, well that's no screamin' he** so out it goes , and now that the galley looks so spiffy, maybe a few other nearby things need an upgrade .

IT :cussing:JUST:cussing: NEVER:cussing: ENDS:cussing: ! ! !

 

[kappykaplan]

........................ then there'll be the faucets 'cause they're startin' to show their age :neutral:, and the sink could also use an upgrade to match the new faucets :cry:, and the drain hose from the new sink, well that's no screamin' he** so out it goes , and now that the galley looks so spiffy, maybe a few other nearby things need an upgrade .

IT :cussing:JUST:cussing: NEVER:cussing: ENDS:cussing: ! ! !

Too funny!!!

 

[Chris Patterson]

Drink my friend. That's right, something very strong. By yourself at the kitchen sink while looking out the window..

 

[Stu Jackson]

IT :cussing:JUST:cussing: NEVER:cussing: ENDS:cussing: ! ! !

That was a truly SUPERB post. Well done, oughta copyright it.

BTW, you're right. My list keeps on getting longer.

Also, Chris is right. :dance:

Just don't call it a toilet, window, kitchen or living room....

Besides, the beer or rum always tastes better either before, during or after your "project>"

Oh, also, don't EVER call it "work."