Shallow well jet pump running continuously, burning up

[Danajac]

I am a new employee at a company, and have been tasked with figuring out a problem with a jet pump.

We have a large, underground tank, which is piped to a shallow-well jet pump (3/4 hp), which is piped to a pressure tank, then through a series of filters, then to a hotwater heater and out. They have now had a second pump burn up, because it ran continuously, and did not shut off when it was supposed to.

We discovered that the threaded pvc pipe coming out of the outlet on the pump had stripped and pulled out. I assumed that this was because the pump was not bolted down (it was just sitting on a board), and had vibrated so much that the pipe stripped out.

First, does it seem plausible that this is the reason why the pipe pulled out?

Secondly, why might the pump be continuously running and burning up? What things do I need to check?

I'm not a plumber, but I think I can follow advice in a plumbing system.

Dan

 

[GReynolds929]

I would assume that the pump ran continuously and burned up because the pipe pulled out.....

 

[Danajac]

I would assume that the pump ran continuously and burned up because the pipe pulled out.....

Was thinking the same thing, but they told me this is the second pump that has burned up. What would be making the pipe pull out?

 

[Valveman]

Jet pumps lose prime or work too close to max pressure, getting the water hot and making plastic pipe soft and pull out. Check for a suction leak. Also check the max pressure your pump model can build and make sure your pressure switch cut off point is at least 10 PSI lower than pump max pressure.

 

[Zanne]

They need to ditch the PVC and go with Stainless Steel. I was constantly having this problem & it caused a pump to burn out. It also let air get in the line through the leaks so my water pressure was crazy & I would get bursts of air.
Not meant as an advertisement, I haven't ordered from them yet, but Stainless Steel pipe fittings, valves, pipe nipples, flanges, tube fittings, and stainless steel pipe - PipingNow.com was recommended to me as having decently priced stainless steel parts. I haven't had the threads break & plastic melt issue since I replaced the inlet side with stainless steel on my jet pump. I have 1-1/4" on inlet and I'm getting ready to replace the galvanized 1" on the outlet side.

While you are at it, might want to upgrade to use a cycle stop valve to extend the life of the pump.

 

[Danajac]

Thank you, Zanne and Valveman. This may be an ignorant question, but would running the pump on 115v while it's set at 230 volts make a difference in any of this? I just discovered that it was set at 230, when it should have been set at 115.

 

[Zanne]

I have absolutely no idea on power settings. Maybe Valveman or an electrician will know the answer to that. Hopefully someone can give you an answer.

I did google it & this answer came up: "Starting a 230v motor on 115v will not harm the motor. However, supplying 230v to a 115v motor will cause it to burn up".

So, if you had it set to 115v while running 230v it would burn it up, but not the other way around. But, that was an opinion from some rando on the internet. I'm hoping you can get a definitive answer from someone here.

 

[Valveman]

Yes if you have the switch on the motor set for 230V and you wire it to 115V the motor will burn up. It just can't spin fast enough to get to 50 PSI and shut off, so it just keeps running at double the amperage until all the smoke is let out of the motor. Once it gets out you can never put that smoke back in.

 

[Zanne]

Thanks, valveman. I wasn't sure if the rando on the internet was right about that so I'm glad you clarified that it was incorrect and it *can* burn up.
So, switching it to 115v setting might help?

I would still replace at least the male threaded nipple going in to the pump with stainless steel instead of PVC though.

 

[Valveman]

I always like a metal pipe screwed to the pump before adding any PVC in case the pump gets hot. But a PVC pipe screwed to the pump will not melt unless the pump looses prime or can't reach the pressure switch shut off point. Even then it is not the PVC pipe that is the problem but the fact that the pump cannot shut off and the water will get hot.

 

[Zanne]

I've read that male threaded PVC tends to strip more easily in metal female threads. The vibrations of the pump can also create heat/friction & break the threads. I had a combo of pump not turning off when there was a leak, pump vibrating, male threaded pvc on the inlet side, & temps over 100° in the well house due to very hot summers & being in a metal shed that acted like an oven. The weather being bipolar doesn't help. 85° in the day and 45° at night... (which just happened here today).

 

[Valveman]

The problem is female PVC threads tend to crack. The tighter you get them the easier they crack. I think metal pipe going into the pump causes more vibration problems. But vibration is not nearly as much an issue as heat. 100F is really not a problem, but if the water gets any warmer from a lack of flow the PVC softens and pulls out.

 

[Zanne]

Reminds me I need to get anti-vibration pads to go under the pump.