Booster on city supply

[davidcaz]

I've seen a few posts here about booster pumps on city supply, but haven't seen anything I can relate to my situation
Set - Up:
Pump: 1 hp FW CPJ10S
Tank: Amtrol WX-252
City Water Pressure: 40-42 static

I have the setup listed above, and the motor bearings are about gone. It squeals like a siren, and does not seem to boost the pressure at all. I've let the pump run, and no change to the (new) pressure gauge. I turn the pump off, and still no movement on the gauge.

This system was installed years ago, when city pressure at the house was very low (end of line on top of hill). Since then, the city pressure seems to have improved quite a bit.

I've had a well service company look at the set up. They will replace the pump and motor for around $1000, with another 1 hp system, but I know I can pull the motor, take it to the local motor electric place, and they will rebuild the motor and rebuild the pump for maybe 200.

Question: Assuming this pump should be set up for 30-50 on/off, (from the FW website) and tank set to 28 psi precharge, will the pump ever even come on, if city water is steady at 40 psi? It seems that if the city pressure and flow are such that if the system never gets to 30 psi, the pump just will sit there. I'd like a little bit more than 40 psi, but don't think I need to hold the system as high as 60 (which this motor/pump doesn't seem to be capable of anyway. ) The house is 50 years old, with lots of old outside irrigation, and I don't want to put more pressure on than I need.

So, if city pressure is stable at 40, and the pump would just sit there most of the time, it sounds like a bad idea to pay 200 to rebuild, and an even worse idea to pay 1000 for a new setup. It also doesn't seem like the right idea to change the cut in to 40 and leave the cutoff at 50. I guess that might get the pump to come on, but wouldn't it be short cycling at that point?
Am I just missing something here? or misunderstanding how it all works?
Any thoughts, Corrections to my conclusions, or ideas on how to get a little more pressure are very welcome

 

[Boycedrilling]

Yes, there is a little bit that you’re not quite understanding . There is a difference in a pump used in a pressure boosting situation with a pressurized intake, and that same pump when it is sucking water in and the intake is actually under a vacuum.

Let’s say your pump is capable of producing 60 psi, with the intake under a suction or vacuum situation with the water level being say 10 ft below the pump. If you look at the performance charts for your pump, it probably lists different flow rates for different depths to the water level.

Now, in your situation, the pump intake is not under a vacuum, but is pressurized. The pump is capable of adding the 60 psi that I supposed above, to the intake pressure. If your intake is pressurized to 30 psi,you could have 90 psi on the discharge. Clear as mud? You can add the intake pressure to the pressure the pump can produce.

Now do you want 90 psi? I doubt it. And yes if you keep the pressure switch at 30/50, the only time the pump would run is if the city water pressure at the pump dropped down to below 30 psi.

If you decide to keep the booster pump, you might want to consider adding a cycle stop valve. Then the pump would run continously under flow conditions and not cycle on and off. You would also see a constant pressure while the booster pump is running. There would only be two times when the pressure would fluctuate. When you quit using all water, the pressure would slowly rise until the pressure switch shuts the pump off. Then when you start to use water, the pressure would slowly drop as you use water out of the pressure tank, until the pressure switch closes, and the pump turns on. The pressure would then rise to the setting of the cycle stop valve and stay at that pressure, as long as you continue to use water.

 

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[ThirdGenPump]

Boyce covered the basics.

The pump should be able to make pressure even with a shot bearing, changing the motor probably won't fix your issue. The impeller is likely damaged as well. A CPJ is an expensive pump for that application. Convertibles are just more expensive because you're paying for the separate jet assembly. Sometimes it's worth paying that cost because an exact replacement is less plumbing, sometimes the price difference is too much and re-plumbing is cheaper.

My preferred set up for booster systems is a Goulds JS series with a cycle stop valve. It'll let you cut out that large tank.

 

[Valveman]

The city pressure coming in at 40 PSI can be used as a low flow by-pass. With a pressure switch setting of 35/55 the pump will not come on as long as the city can maintain 40 PSI. So the pump will not run for small things like brushing teeth, filling an ice maker, or flushing a toilet. However, when a larger demand is required like a shower or irrigation sprinklers, the pressure will drop from 40 to 35, and the pump will be started. With a CSV set at 50 PSI, the system will then maintain 50 PSI constant for as long as the shower or sprinklers are running. When the sprinklers are turned off, the CSV will allow the little 4.5 gallon size tank to fill to 55 PSI, the pump will shut off. The pressure will again work at 40 PSI city pressure, saving wear and tear on the pump, when low flow rates are being used.

I also like the Goulds J and JS series for these applications.