Questions about proposed deep well pump replacement and appropriate component choices

[tdcody]

Hello all - long time lurker - I have learned a lot about scenarios somewhat different than my own and would greatly appreciate any guidance this community can provide.
I am the new owner of a water well-supplied home in San Diego County - very high wildfire risk, so we have the required 10,000 gal galvanized storage tank which serves the home (including automatic fire sprinklers), large irrigation system, and fire hydrant. This is my first experience with a well!

Well info (all specs from original driller report): drilled 2003, 900' deep, depth to 1st water 675', static water level 380', 20' of 6.5" steel casing, then remainder 4" PVC casing (alternating screen/solid) to the bottom. Original production was 29gpm in 2003, currently 13gpm.

The well most recently (until this morning) housed a 2008-model year submersible 5hp 10gpm single phase motor/pump, piped uphill about 200' vertical rise to the 10,000 gal storage tank, with adjacent pumphouse. In pump house is a very large booster pump (also 5hp) charging two ~80gal expansion tanks, which then supply the house (including automatic fire sprinklers) and irrigation circuits. The fire hydrant is connected directly to the storage tank with a large-bore pipe. Aside from the well pump's integral check valve, there is another check valve at the top of the well (horizontal) and a third at the base of the storage tank at ground level just before the fill pipe climbs up to the top of the tank. Both inline check valves were replaced a few months ago after water hammer (I think) caused the PVC pipe to break just past the well and that first inline check valve. There is evidence of prior repairs to the pipe at that location.

Well pump stopped running and was found to be drawing very high current (up to 80A, intermittently tripping overload), so frozen pump was suspected. It was pulled today (very cool to watch!) with the following findings:
1) pump not locked, but has intermittently significant resistance to turn by hand.
2) several sections of galvanized drop pipe were corroded substantially, one with several small penetrations.
3) 2/3 flat submersible cable had water inside the outer insulation sleeve and also within the individual wire's insulation, with surface oxidation of the stranded copper wire inside - all four wires affected through at least the bottom 25', after which I didn't cut it open further.

Well company (new to me) is proposing install of the following:
Pump: 10GS50 Goulds 10GPM 5HP 42 stage 4" pump ($3200)
Motor: M50432 Goulds CentriPro 4", 5 HP, 230 Volts, 3 Phase motor ($2300)
Driver: 136X1213 Danfoss VLT Aqua-Drive 7.5HP/5.5kW 230V single phase driver ($4900)
Cable: 4/3 flat submersible cable, 870' ($10,100)
Drop pipe: replace six corroded galvanized pipe sections with Sch 120 PVC ($1030 material cost)
+ labor (pull old stuff, install new stuff)
+ supplies
Total: ~$24,500
1 year labor warranty, 3 year manufacturer warranty on pump/motor, shorter warranty on the driver.
Company states expected life of the well motor/pump is 5-10 years.

Short-term goal: restore the system's functionality and future-proof as much as is reasonably possible in terms of well components, including trying to get more life out of the down-hole hardware than 5-10 years, which seems like it should be possible. I am shelving the booster pump/pressure tank setup for now, which I plan to overhaul and redesign in the next 8-12 months (unless it fails sooner).

I have many questions! I will limit myself to the major ones:
1) is this a reasonable setup in general?
2) I am unsure how to weigh the pros/cons of the recommended VFD upgrade given the giant unpressurized storage tank upstream of the booster and pressure tanks, and therefore much less benefit for constant pressure supply from the well pump. I see the benefit in a VFD setup for a new booster pump.
3) am I in the right ballpark with 5hp/10gpm submersible pump size to begin with?
4) is the water intrusion/corrosion of the submersible wire a common problem, or a fluke due to some kind of old amateur mistake that is not likely to be repeated with professional work?
5) Cost!! I understand that most of these components are priced at close to or over 2x retail cost elsewhere. The wire/cable pricing is particularly hard to swallow. Labor looks underpriced, comparatively. They do not want to install anything they aren't providing. I understand the need to build costs and profit into materials, but this seems a bit insane. Plus I don't see much insurance with the 1 year labor warranty. I want to be fair but not get scammed.

Thank you in advance for any advice. I cannot contribute expert well/plumbing info, but I can offer veterinary info for those of you with furry friends.

Sincerely,

Dave

 

[Reach4]

What provides the pressure to the house-- the well pump, or does the house water come from the galvanized tank?

How high up is the galvanized tank?

That variable frequency setup is more complex and may be less reliable than a conventional on-off pump.

 

[Sponsor]

 

[Valveman]

Unfortunately, you will need the 10GS50 to get 12 GPM from 800' deep. However, when the water level is at 380', there is not enough head on that pump to keep it happy. Upthrust could be one reason for it early demise. I would install a 12-13 GPM Dole valve at the surface to keep the pump on its curve, which will also fall in line with the production rate of the well.

Setting the pump in well at 800' in 4" casing could also be a problem. Since static is 380' and first water is 675', the water will be going down to enter the pump. A top feeding situation without room for a flow inducer on the pump can cause the motor bearing to overheat and shorten the motor life. It would be good to know if the stick up on the old motor was down from the required 1.5" height from the motor face. If the shaft does not stick up 1.5", the bearing got hot. Really the only remedy for this is to not set the pump so deep, and some times you do not have that option. But if the water is coming in at 675' or lower, and the pumping level never gets below 675', I would set the end of the motor at 674' to get proper cooling for the bearing. If the old bearing is still 1.5" stick up, then top feeding is not a problem.

Nothing wrong with the 10GS50 pump. But I would use a 5HP, 230V, single phase Franklin motor instead. Goulds is getting better, but I still think Franklin has the best motor.

With the single phase motor you will need larger, #2 wire. But it will be worth it as you will not need the troublesome, expensive, and sort lived VFD. This will make more difference in how long it last and how much it cost you then anything else. The VFD is a money maker for the pump installer and manufacturer, but that is not a good thing for you.

Notice that the pipe that was wrapped in pipe wrap or electric tape did not rust. It is time consuming, but you can tape all the steel
pipe that is below the water level. Pipe seems to rust the worst at the static level, as that is where it gets the most oxygen. Sch 120 PVC is great, as long as you use "double jacketed" wire, which is more expensive, but worth it. The torque from a 5HP, even with a VFD will wear the wire with the flex of the plastic pipe, Torque arrestors and stand offs don't help, double jacketed wire does.

Then the booster pump can be sized for the irrigation and fire sprinklers. A 5HP would be a very large booster unless the pressure is higher than 40/60 or you need more than 100 GPM. But whatever size booster you need it will work better, last longer, and cost much less if you control it with a Cycle Stop Valve instead of a VFD. Both deliver constant pressure. It is just a matter of whether you want inexpensive, long lasting, and reliable like the CSV offers or not.

Oh and BTW, if the length of warranty matters, you haven't chosen the right stuff.

 

[tdcody]

What provides the pressure to the house-- the well pump, or does the house water come from the galvanized tank?

How high up is the galvanized tank?

That variable frequency setup is more complex and may be less reliable than a conventional on-off pump.

Thank you for the advice- reliability is the #1 priority for sure. The folks who make and sell VF components aren’t going to list their weaknesses, so I appreciate it.

The galvanized tank is about 200’ higher than the well (on a steep slope, so total distance is about 300’).
Well pump fills the galvanized tank (non-pressurized). Then the booster pump pulls directly from that tank and fills two 82 gal pressure tanks, which feed the house.

So pressure to the house is provided by the booster pump. The well pump just has to overcome the additional 200’ rise to the unpressurized galvanized tank.

Thank you!

 

[tdcody]

Unfortunately, you will need the 10GS50 to get 12 GPM from 800' deep. However, when the water level is at 380', there is not enough head on that pump to keep it happy. Upthrust could be one reason for it early demise. I would install a 12-13 GPM Dole valve at the surface to keep the pump on its curve, which will also fall in line with the production rate of the well.

Setting the pump in well at 800' in 4" casing could also be a problem. Since static is 380' and first water is 675', the water will be going down to enter the pump. A top feeding situation without room for a flow inducer on the pump can cause the motor bearing to overheat and shorten the motor life. It would be good to know if the stick up on the old motor was down from the required 1.5" height from the motor face. If the shaft does not stick up 1.5", the bearing got hot. Really the only remedy for this is to not set the pump so deep, and some times you do not have that option. But if the water is coming in at 675' or lower, and the pumping level never gets below 675', I would set the end of the motor at 674' to get proper cooling for the bearing. If the old bearing is still 1.5" stick up, then top feeding is not a problem.

Nothing wrong with the 10GS50 pump. But I would use a 5HP, 230V, single phase Franklin motor instead. Goulds is getting better, but I still think Franklin has the best motor.

With the single phase motor you will need larger, #2 wire. But it will be worth it as you will not need the troublesome, expensive, and sort lived VFD. This will make more difference in how long it last and how much it cost you then anything else. The VFD is a money maker for the pump installer and manufacturer, but that is not a good thing for you.

Notice that the pipe that was wrapped in pipe wrap or electric tape did not rust. It is time consuming, but you can tape all the steel
pipe that is below the water level. Pipe seems to rust the worst at the static level, as that is where it gets the most oxygen. Sch 120 PVC is great, as long as you use "double jacketed" wire, which is more expensive, but worth it. The torque from a 5HP, even with a VFD will wear the wire with the flex of the plastic pipe, Torque arrestors and stand offs don't help, double jacketed wire does.

Then the booster pump can be sized for the irrigation and fire sprinklers. A 5HP would be a very large booster unless the pressure is higher than 40/60 or you need more than 100 GPM. But whatever size booster you need it will work better, last longer, and cost much less if you control it with a Cycle Stop Valve instead of a VFD. Both deliver constant pressure. It is just a matter of whether you want inexpensive, long lasting, and reliable like the CSV offers or not.

Oh and BTW, if the length of warranty matters, you haven't chosen the right stuff.

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Valveman- thank you!!! This is immensely helpful and answers many of my questions. I truly appreciate it.

I will inspect the motor shaft to deduce the bearing’s history- that is a very clever and simple test, i.e. the best kind!

It sounds like the cost difference between the different wire gauges just about offers the difference in price between VFD and conventional setups, and the VFD brains are on the surface so don’t require $$$ to inspect or install. So my goal here would be to choose the setup which is likely to give me a longer lifespan for the motor/pump. It sounds like the CSV is the right choice for conventional setups for both the well and booster pumps, so I will definitely include them for a conventional setup. It looks like an incredibly useful product.

The tips for the well pipe are also very helpful. I am planning double-wrapped wire, so it sounds like this gives me options for either pipe material which is easier.

I am glad to hear your assessment of the value of a warranty- I completely agree!

The diagrams of the setups are also helpful- I can understand the options very clearly.

THANK YOU for taking the time to write such a thoughtful and useful reply. I really appreciate it.
Dave

 

[Reach4]

If the galvanized tank is 140 ft or so above the house, no pressure pump would be needed. Gravity would give about 60 psi.

If you could find a 2 HP 5 gpm pump, that would probably do the job. No need to fill your big galvanized tank at 10 gpm. Works with lighter gauge wire.

I am finding 1.5 HP 5 gpm pumps, but I have not found a 5 gpm 2 hp yet. It may be that your water will not drop to 800 ft, so the 1.5 HP 5 gpm pump would be quite sufficient.

 

[Valveman]

With the storage tank being 200' in elevation above the well head, you need to add that 200' to the lift of the pump. With static at 380' that would be a minimum head on the pump of 580'. When/if the water level pulls down to 800', that would be 1000' of head on the pump. With the 10GS50R that would mean no Dole valve necessary. But with the 10GS50 the Dole valve is still needed.

Like Reach says, you can switch to a smaller well pump. A 5GS20 would still pump 2 GPM from 1000' of head and 7 GPM from 580' of head. At 3 GPM average that would be 4,320 gallons per day. If that will satisfy the demands the 2HP should be much less expensive and last much longer. Franklin says their 2HP and smaller "Super Stainless" motors do not require a flow inducer or cooling shroud. The idea being that the motor is so short the bottom gets sufficient flow to keep cool even in a top feeding application. The 5HP certainly can't do that, which is why I assume you will find the thrust bearing has dropped to less than 1.5" shaft stick up.

The booster pump still needs to be sized to match the fire sprinkler zone and/ or the irrigation. I doubt that a 5HP, 100 GPM pump would be needed, but would still work if necessary. At 40/60 pressure an 82 gallon size pressure tank holds 20 gallons of water, two would hold 40 gallons. That is not nearly enough tanks for a 100 GPM pump unless you have a Cycle Stop Valve. Then if you do have a CSV, those two tanks are more than you need. One is still more than needed but that would let you keep the other disconnected for a spare if needed later on.

 

[tdcody]

With the storage tank being 200' in elevation above the well head, you need to add that 200' to the lift of the pump. With static at 380' that would be a minimum head on the pump of 580'. When/if the water level pulls down to 800', that would be 1000' of head on the pump. With the 10GS50R that would mean no Dole valve necessary. But with the 10GS50 the Dole valve is still needed.

Like Reach says, you can switch to a smaller well pump. A 5GS20 would still pump 2 GPM from 1000' of head and 7 GPM from 580' of head. At 3 GPM average that would be 4,320 gallons per day. If that will satisfy the demands the 2HP should be much less expensive and last much longer. Franklin says their 2HP and smaller "Super Stainless" motors do not require a flow inducer or cooling shroud. The idea being that the motor is so short the bottom gets sufficient flow to keep cool even in a top feeding application. The 5HP certainly can't do that, which is why I assume you will find the thrust bearing has dropped to less than 1.5" shaft stick up.

The booster pump still needs to be sized to match the fire sprinkler zone and/ or the irrigation. I doubt that a 5HP, 100 GPM pump would be needed, but would still work if necessary. At 40/60 pressure an 82 gallon size pressure tank holds 20 gallons of water, two would hold 40 gallons. That is not nearly enough tanks for a 100 GPM pump unless you have a Cycle Stop Valve. Then if you do have a CSV, those two tanks are more than you need. One is still more than needed but that would let you keep the other disconnected for a spare if needed later on.

Reach and Valveman - thank you both again. I checked the motor shaft and (perhaps surprisingly) has the correct 1.5" stick up. I don't think this matters for the smaller motor given its tolerance for top feeding, but good to know?

Yes, 3 GPM average will be plenty for us with the gigantic reserve in the 10k gal storage tank. It sounds like this is an ideal option. I am going to go with the 5GS20, an appropriately-sized Franklin motor, and 6/3 flat heavy-duty (double-jacketed) submersible pump cable. Once that is all up and running, I will plan to redesign the booster pump setup with a cycle stop valve.

Thank you so much for your help!

Sincerely,

Dave