Well casing depth

[jason robinson]

I have a well drilled in early 70s. It has always had an above ground jet pump (75' deep line). I am thinking of replace it with a submersible pump. I will verify well depth but was told about 200 ft. I have water 25' from ground level but have no idea how deep the casing extends. How can I determine how deep the casing is? I saw some things about using magnet but I don't understand the concept since at some point the magnet is going to hit the side of the casing before it reaches the bottom. Overall goal is to determine how deep the pump should be.

 

[Reach4]

So your casing is steel. Even if it were PVC, a magnet would not be a useful tool to know the depth of the well. If your casing is 4 inch steel, it would probably be best to use a "3-inch" Grundfos SQ pump. What diameter is your casing?

If practical, it is usually best to put the pump at least 20 ft above the bottom. Did you ever run short of water with the foot valve 75 ft down?

Best would be to check county records. They may record how deep the well is. Or if you know the driller, ask the driller, or if retired, ask around to see who got his records.

What will you use for drop pipe? If 1 inch SIDR polyethylene, you could put the piping down and use it like a dipstick. If you hit bottom, mount the pump 20 ft higher.

Do you get freezes? If so, you might consider a pitless adapter, even if that is not common in your area. Even if it does not freeze in your area, a pitless adapter may be advantageous. It's analogous to having a connector for electric wires rather than splicing wires.

 

[Sponsor]

 

[Valveman]

Probably don't need to set the pump any deeper than the ejector on the two pipe jet pump. Setting the submersible below the well screen can cause the motor to overheat. 3" pumps are good but 4" pumps will fit in 4" casing if the casing is still good and not too rusty. Just a weight on a string is good enough to get a well depth after you get the pump and pipe out of the way.

 

[jason robinson]

Never ran short of water but always seem to have issues with the above ground pumps. No silt appears in water but I keep shearing impellers (every couple years). Casing appears to be 6". That's what it is at ground level and I can't see any downsizing looking down the well. Going to use 1" poly for the pipe and doesn't really freeze ( at least nothing a light in well house won't prevent, this is central GA). I was hoping to find out casing depth an put pump just above that. I'm a layman and not sure it even matters. I was initially thinking if well is 200' I'd probably go 150' and call it good enough. Probably going to need 1/2 hp 10 gpm pump but not super confident on my numbers for that. Water 25' in well, house is 10' higher than that. 60' horizontal run to house. Currently looking at AW Mcdonald and F&W stainless pumps but open to recommendations near that price range. I can check with county but I'm not specific on the year or date and I'm sure I'll get the run around since it's all paper files probably stacked in basement somewhere.

 

[Reach4]

Never ran short of water but always seem to have issues with the above ground pumps.

I would think 3/4 hp 10 gpm might be a better match. A flow inducer (sleeve) would be good. Easy and cheap.

 

[jason robinson]

I'm not sure I'm calculating head correctly but I'm getting around 150 (full capacity) and 230 (75' drop in water level).

 

[Valveman]

If your water level drops to 150' you will need a pump that can do 300' of head to work with a 40/60 switch.

 

[jason robinson]

I'm really hoping the recovery rate is good. Since it is only under 50' of water now and never had issues running out (for past 40 years). Maybe they just didn't use much?? This is a rental house so new people will have new water demand. I'll do a recovery rate test before I purchase anything.

 

[Valveman]

The pump is only lifting from the actual water level no matter how deep you set the pump.

 

[jason robinson]

Understood. What I'm basically trying to do is determine the min and max head. So min water depth 25' from surface (160ish head??), max depth today is 75' (215ish head??) from surface (depth of existing foot valve). By 50' of water I meant that is all the water that can be used today. So 70ish gallons is all the current well will deliver without any recovery. I'm assuming 70 gal isn't that much for a house so thinking the recovery rate must be fairly high. I'm renovating the house for the next few months so got time to do some testing on it. Either way I'm sure I'll go with your recommendation of 3/4 hp. After looking again the 1/2hp might cause GPM issues if water level ever drops.

 

[Valveman]

Always figure worst case or deepest depth to water.

 

[Reach4]

Always figure worst case or deepest depth to water.

Except that a significant fall off in gpm as the water drops to the pump is somewhere between ok and desirable.