freshwater pump puzzle: pressure switch?

[eagleswing]

we have a jabsco freshwater par-max pump, #17050, 8.7 gallons/minute, multiple outlet. this weekend, I noticed that the pump did NOT shut off when the water tank was empty, but continued to run . we shut off the pump manually, we then filled the h 2 0 tank. we turned the pump on after giving it an overnite rest. now the pump makes its usual noise and runs, but instead of getting 8.7 GPM, we were at 1 teaspoon per minute and a lot of air hissing out of the faucet sink tap. the pump filter and inlet lines look clean and fine, the w ater tank is 1/2 full and is a gravity feed into the pump. this pump has a thermal overload switch on the motor which is an auto-reset , and also a pump pressure switch to shut off the pump if the water level is too low . (or nonexistent ) (as in , 'someone's ' shower accidentally drained the whole water tank and 'someone' forgot to shut the freshwater pump off despite there being no h 2 0 in the shower...) ...)

does anyone know whether a bad pressure switch will cause this pump behavior ? it's a 10 pound cost to replace the switch but a 100 pond cost to replace the whole pump...

any and all thoughts welcome...

 

[dt4134]

The pressure switch won't cut out the motor when the tank is empty. It's on the output side.

I fitted a par max 2.9 this spring. It does say it can run dry without damage but I have no idea how long it will do that for.

I presume if you have an accumulator it'll take a while to get the air out of the system.

 

[Seadog17]

we have a jabsco freshwater par-max pump, #17050, 8.7 gallons/minute, multiple outlet. this weekend, I noticed that the pump did NOT shut off when the water tank was empty, but continued to run . we shut off the pump manually, we then filled the h 2 0 tank. we turned the pump on after giving it an overnite rest. now the pump makes its usual noise and runs, but instead of getting 8.7 GPM, we were at 1 teaspoon per minute and a lot of air hissing out of the faucet sink tap. the pump filter and inlet lines look clean and fine, the w ater tank is 1/2 full and is a gravity feed into the pump. this pump has a thermal overload switch on the motor which is an auto-reset , and also a pump pressure switch to shut off the pump if the water level is too low . (or nonexistent ) (as in , 'someone's ' shower accidentally drained the whole water tank and 'someone' forgot to shut the freshwater pump off despite there being no h 2 0 in the shower...) ...)


does anyone know whether a bad pressure switch will cause this pump behavior ? it's a 10 pound cost to replace the switch but a 100 pond cost to replace the whole pump...

any and all thoughts welcome...

Sounds like it might just need priming. If it's pumping air it should pump water.

Either that or there is an air leak in the suction pipe.

 

[VicS]

I cannot find any details of your pump but ITYWF that it should self prime. Are you sure about the number 17050 ( maybe the trouble is its an American number and/or model)

Assuming its a diaphragm type of pump
I'd suspect some dirt from the tank has become lodged in the valves, despite there being an inlet strainer.
I'd strip it down and clean the valves.

Consider fitting a " valve kit " and perhaps also a "diaphragm kit".


If the pump actually runs total replacement is not likely to be necessary ... just overhaul.
Some people would say ( have in the past said) fit a new one and overhaul the old one to keep as a spare.

I agree there is no reason to suspect the pressure switch but if there is a tank level sensor that should have shut the pump down before emptying the tank it requires a looking at!

 

[cliff]

Remove the outlet form the pump and switch on - this is often enough to blow any debris clear of the valves - if no joy open the pump and clean the valves manually.

 

[nimbusgb]

When this happened to my system I found a large amount of calcium deposit in the tank blocking the outlet to the pump.

Disconnect the input side of the pump and make sure that gravity really IS feeding water to the pump

 

[Liz_I]

Probably the easiest thing to try is to turn your pump off. Open all taps, turn the pump on wait for the bubbling and hissing to stop and then turn the taps off.

We have fitted a light which comes on when the pump is cycles. The water pump makes a noise when there is water but goes silent when it runs out If the light stays on we know there is no water, simple but effective.

Hope you get it sorted.

 

[Adamastor]

I'm with Nimbus on this! IMHO, if one of the valves gets stuck, there is no seal on the pump, so none of the multiple pump chambers work. Take the head off and check under the valves before coughing up for a spares kit.

 

[KellysEye]

>I noticed that the pump did NOT shut off when the water tank was empty, but continued to run

If it does that make sure you switch it off smartly or the motor will burn out, as I found. It sounds like one of the diaphragms at the bottom of the pump has split. Take the bottom plate(s) off and check if that's the case. Then buy a service pack and replace both diaphragms.

Please let us kmow how you get on.