Low GPM well pump

[CAD]

Based on the date code my Sta-rite VIP III well pump controller, I have a ~34 year old well pump. The controller is model VIP4D02-07, which from what I gather would correspond to a 3/4HP well pump. The well record shows total bore depth of 155 ft, and a static water level ~88 feet below grade in 1965, however, I live in an area where the water table appears to have risen significantly with the departure of manufacturing since then. Based on the well my neighbor just drilled ~100' from my well, the static level is probably more like 63 feet below grade currently. Drawdown when pumping was only 2' when pumping at 25gpm for 24HRS when the well was drilled in 1965. When the pump kicks in at 30 psi and I have a hose bib faucet wide open with a short 10' x 5/8" garden hose attached to it, I am only getting roughly 5 GPM from the running pump, with the pressure stabilizing at ~38 psi. Based on some Franklin pump curves I looked at, I'd expect more gpm for a 3/4HP pump with a Total dynamic head ~158 ft at 5 gmp for my system (assuming total equivalent pipe length of ~200' of 1" steel pipe at the end of the hose and the 38 psi at the pressure tank). For the depth of my well, I'd figure a 3/4HP pump would be an original 10 or 15 GPM pump, and I'd expect to get more like 10 GPM vs. what I observed.

Wondering if I should consider replacing this pump now based on the above? Or if I am possibly overlooking something in figuring what the flow rate should be. Also, is this amount of reduction in flow typical for an old pump?

 

[Reach4]

You may have a 7 gpm 3/4 inch pump. If the water level is high, that puts out significantly more than 7 gpm. You are likely limited by the hose and hose spigot. If you are limited by the pump, the pump will not be cycling. The water pressure will stay steady at the pressure switch, pressure gauge and pressure tank..

If the pump works, I would not replace it. But if the control box has been in service for 10 years, I would replace the start capacitor.

What ID is your well? Is it PVC or steel? If 4 inch steel, and I was replacing the pump, I would use a Grundfos SQ pump. (3-inch pump)

 

[Sponsor]

 

[CAD]

The well is 6” diameter, steel cased until the sandstone bedrock roughly 55’ down, after which there is just the 6” diameter drilled hole in the rock to 155’. Im not sure on the drop pipe construction, but am assuming 120’ of 1” steel pipe. The top of the casing contains a Whitewater Pitless Adapter Tank.

The pump does not cycle with the hose spigot fully open, and the pressure stabilized at 38 psi at the pressure switch with it running. I ran it for 20 minutes with no change in pressure, and measured the flow several times during this period, and got the same 5 GPM.

 

[CAD]

Also, I took off the cover to the controller, and on the backside it is noted that the pump is 3/4HP and model no. 8P-SPQ (this is all it says, no manufacturer). No luck with a Google search on this model number from a pump installed in 1989.

 

[Reach4]

The pump does not cycle with the hose spigot fully open, and the pressure stabilized at 38 psi at the pressure switch with it running. I ran it for 20 minutes with no change in pressure, and measured the flow several times during this period, and got the same 5 GPM.

Another way that could happen is if there is a CSV preventing cycling. How big is your pressure tank?

 

[CAD]

Not sure on the size of the tank, but I’d imagine it is the smallest 95 gallon one. There is not a csv on my system.

 

[CAD]

Did some additional testing today. Draw down on the pressure tank was around 13 gallons, so I’m thinking it is more like a 60 gallon tank. It takes the pump almost 4 minutes to fill the 13 gallons, so it’s only making 3.3 GPM when just filling the tank. I now think there may be an issue with the drop pipe, either has holes or the bleeder valve is not functioning properly any more.

 

[Valveman]

Check motor amps. If it is drawing 7 amps you probably have holes in the drop pipe. If it is drawing less than 7 amps the pump maybe worn or the flow restricted like a clogged screen.

 

[CAD]

Can I reuse the current control box (Sta-rite VIP III, model VIP4D02-07, 3/4 HP CSCR-type, 59mfd start cap, 23mfd run cap) if I replace the pump with a 3-wire Grundfos 10s07-12 (3/4 HP MS402 motor)? The control box noted by Grundfos for this motor/pump is a CSIR with a 95mfd start capacitor.

 

[CAD]

Correction, looked in the box and the start capacitor is actually 88-105 mfd, so different than the tables currently shown by Pentair for the newer 3/4 HP VIP control boxes.

 

[Reach4]

If you do reuse an old control box, I would replace the start capacitor anyway. Those are non-polarized electrolytics, and they are destined to fail.

Do you have an above-ground check valve? If not, a leak in the downpipe should cause pump cycling.

 

[CAD]

If you do reuse an old control box, I would replace the start capacitor anyway. Those are non-polarized electrolytics, and they are destined to fail.

Do you have an above-ground check valve? If not, a leak in the downpipe should cause pump cycling.

Yes, with the type of tank I have (whitewater PAT) there is a check valve just below the Pitless spool, and bleeders just below that to inject air into the tank each time the pump cycles.

 

[CAD]

Comparing CS vs CSCR control boxes offered by goulds/xylem (from what I gather the current CS box offered by grundfos is made by xylem) the start capacitors are smaller in the CSCR boxes for the same motor HP. For example, CS only box for 3/4 hp list a 86-103 mfd start capacitor, where as the CSCR box lists 59-71 mfd start capacitor. I’m wondering since my current CSCR box is for 3/4 HP but has the CS size start capacitor if I should switch to the smaller listed size (59 mfd is listed by both Pentair and Xylem, vs the 88-105 currently in the box)? Will the larger start capacitor create issues for the motor in the CSCR box? Trying to make sense of this.

 

[Reach4]

A CSR box has two capacitors, a start cap and a run cap. During start, they are electrically in parallel, and the net capacitance is the sum. Then the start cap is disconnected in effect, and only the run cap stays connected.

So it would make sense that the sum of the two caps in a CSR box would be similar to the capacitance of the single cap in the CS box.

Regarding your question, I doubt the values are that critical. But I am not going to give you a direct answer, since I am not sure.