Pump Controls Issues on Pump acting as Booster

[Osage Hills Craig]

History
I've had a pump house for 22 years that is directly attached to the rural water main. This pump boosted the pressure because the main is about 120' below the house. This pump house is roughly 45' below the house. The builder installed a 1.5HP shallow well pump, with a bladder tank (set at 68psi), and a 80-100psi switch (set at 70-90). This setup delivered 55psi at the house. This setup worked fine when there was adequate water fed from the main. We live just outside of town and the sub-division nearest us seems to be prone to main breaks. So, when there is a main break the standard pressure switch just kicked on and the pump never stopped. We'd have to realize we had no water and cut the breaker (to keep from burning the pump up). A few years ago, I installed a Cycle Stop Sensor (https://cyclestopvalves.com/collections/cycle-sensor-pump-monitors) to detect a dry pump situation. This seemed to provide relief from main breaks, but now it seems that with the additional houses in our area, the main pressure drops during the summer and it will pause the pump several nights a week in the early evening.

Second Pump House
Last year, I installed a 2nd pump house (on another part of our land), and I put it underground with a 300 gal. storage tank to act as a cistern (tank is in the same concrete enclosure as the pump) between the main and the pump. It has a similar pump and pressure tank; and it works perfect. The tank is at the same level as the pump, with the outflow from the bottom of the tank, so the pump is not having to draw the water. It's located closer to the top of the hill, so it runs on a 60-80psi switch.

The new pump setup works so good, I've tried to retrofit the 22 year old setup. It's not practical to bury the whole pump house, so I just purchased an underground cistern tank (300 gal.). The cistern is buried just outside the pump house and the height of draw, from the pump to the bottom of the tank is less than 6' (well within the 25' limit of a shallow well pump). The tank was designed to be buried and the inlet/outlets are at the top. Inside the tank on the pump side, I've put a 1" copper tube to the bottom of the tank with a "well foot" at the bottom. The "well foot" has a metal filter and a check value.

Retrofit Situation
After priming the pump, the new system has no problem pumping water. I've even opened the valve to go up to the house and the house seems to get plenty of pressure (No, I have not measured the PSI yet). The problem is that the pump will NOT shut off. The well foot maintains prime, so the pump can be manually switched on/off and produces plenty of water.

I thought that perhaps some rust had fouled the switch as the pressure gauge seemed to want to dance. I put a replacement pressure switch and gauge on and I get the same result, although the gauge is stable now. I've checked the bladder and it is still at 68psi (so I'm assuming the bladder is still OK). I haven't adjusted the 80-100 switch down to 70-90; but I only see about 75psi on the gauge.

Is this a limitation of the pump having to siphon the water up 6 feet?

 

[Bannerman]

Is this a limitation of the pump having to siphon the water up 6 feet?

From your description in the History section, the purpose of the pump was only to further boost the pressure to compensate for the 120' (~51 psi) rise in elevation from the water main to the house. That pump didn't need to actually draw water vertically as the water main supplied the pump under some pressure after rising 75' to the pump inlet. Assuming the mains pressure was 52 psi or greater, even if the pump was shut off, water would likely continue to flow to the house, but the pressure and flow rate without the boost would be quite low.

In the 2nd situation, that pump is also not required to draw water as the 300 gallon cistern is also supplying pressurized water directly into the inlet of the pump.

In the retrofit situation, the pump is no longer boosting pressure directly from the water main, but now must draw water under negative pressure from the buried cistern, and then push that water vertically 45' to the house. You haven't specified which pump you are using but it sounds as though it is now doing more work with being forced to draw from the cistern.

If the pump is only capable of acheiving 75 psi after drawing from the cistern, then in using a 80/100 or 70/90 pressure switch, the upper cut out pressure will not be achieved and the pump will not shut down. If the pump can only acheive 75 psi, then the pressure at the house after the 45' additional rise will be at best 35/55 psi. The pressure to the house will probably need to be actually less, particularly when the cistern is not fully filled as water will need to be drawn a greater distance vertically. To ensure the pressure switch cut out pressure will always be satisfied, may require a 45/65 pressure switch.

To deliver higher pressure to the house, you may want to consider a submersible pump with a higher head rating, placed directly within the cistern. A submersible will be more efficient and will not require priming as it will be only pushing water forward, out from the cistern.