Depth of pump below static level?

[Odysseus99]

Drilled a well, don't yet have a pump, may do it myself, researching how-to.

The info- 400 ft deep well with 6 inch steel casing all the way, static level at 290 ft from top, producing clean water from rock at 30 gpm. Will be pumping to a holding tank (not pressure tank) that is 35 ft above the grade at the well. With 200 ft of 1 inch pipe from the top of the well to the tank, and another 300 ft to static water level that's 500 ft of pipe or more. Will use a 5 or 7, maybe 10 gpm pump, not sure yet.

Question is- how far below static water level should the pump be located? I'd prefer deeper as drought insurance, but does it damage the pump to place it deeper?

 

[LLigetfa]

You need to know the pump curve and the well recovery rate. It is the water level that matters to the pump not the depth it is hung.

 

[Sponsor]

 

[Reach4]

20 feet above the bottom is fairly standard for an initial pump placement from what I think I remember reading.

Pump power should be good and efficient from the static depth 290 to maybe 350 , but it would be good IMHO if the pump could produce some water from 470 or 460 pressurized to your house in case you get that drop you are worried about.

 

[Valveman]

The only reason for a "holding tank" or cistern with a booster pump is if the well is a low producer. If the well makes 30 GPM you don't need a "holding tank" and all the complications and expense that goes with it.

 

[LLigetfa]

Pump power should be good and efficient from the static depth 290 to maybe 350 , but it would be good IMHO if the pump could produce some water from 470 or 460 pressurized to your house in case you get that drop you are worried about.

I don't know how you say "should be good" since the OP did not say what HP or model of pump. Are you clairvoyant?

 

[Reach4]

I don't know how you say "should be good" since the OP did not say what HP or model of pump. Are you clairvoyant?

Forward thinking. I was suggesting that he try to select a pump that could pull some water in drought conditions, even though that deeper depth was on the left side of the pump curve. And that he wanted to select a pump that was in the sweeter middle and maybe middle-right area of he curve for higher water levels.

For example, in this graph a 1.5 HP 20 stage pump could draw water at maybe 4 GPM from 470 with 50PSI pressure (=115 feet of head). The 1 HP would have been ideal with water at 290 or 300 ft and OK if the water stayed no deeper than 350.

 

[Craigpump]

In Cali, lots of people have large tanks so they have water on hand to fight fires.

 

[LLigetfa]

Makes sense, and if you are irrigating with it, tepid is better.

 

[hj]

The pump has to be below the point where the well can maintain the level, depending on how much water is being removed from the well. Extra depth will not damage the pump, running dry WILL, however.

 

[hj]

quote; In Cali, lots of people have large tanks so they have water on hand to fight fires

Yes, but they are called "swimming pools, not "large tanks".

 

[Craigpump]

Those are cement ponds...

Seriously, when we did water wells in SD county back in the 70's, every customer requested a large atmospheric tank

 

[Valveman]

quote; In Cali, lots of people have large tanks so they have water on hand to fight fires

Yes, but they are called "swimming pools, not "large tanks".

I didn't notice the OP was from CA. Yes they require a storage tank for fighting fires. Another one of those extra laws CA has so many of.

No wonder all my CA relatives are moving back to Texas after 50+ years. RIP for the land of milk and honey.

 

[Odysseus99]

Thanks for all the replies, some of which were actually relevant to my original question. All I wanted to know is if it damages the pump to locate it as low as possible, I take it that it does not. That pump is going to be in 90 feet of water at least. After the current drought is over the static level may come up in which case it will be deeper. I want it deep as possible in case of a worse drought later.

Indeed here in CA a 2500 gallon tank is required on the property to have a residence. It is not, however, required to be kept full of water, so some people don't bother, and sometimes they end up pouring their motor oil and coolant into the thing so they don't have to pay recycle fees. Imagine the look on the pumper truck operators face when he realizes he's pumping motor oil onto a forest fire. Oh well.

Any hoodle I'm off grid so I can't use a pressure tank anyway unless I want to buy a huge solar system or leave a generator running 24/7 which isn't going to happen. Property is sloping so I can operate off gravity feed, works fine so far. Been collecting rain water.

So, next question- do you think I can use a poly down pipe in this situation? Pump will be 380 ft below the pitless adapter, static level at 290 feet to grade, storage tank 35 feet vertical height from grade at well, total 200 feet of 1 inch pipe from well to tank. There is a local supplier that I can get 260 or 300 psi poly pipe from special order, if nec.

A little math- 290 ft plus 35 plus 15 feet or so for pipe resistance puts me at 340 feet. People say poly is okay to use at 300 feet, so Im pushing it I guess. But at 340 feet pressure at the bottom of the pipe will be in the 160 psi range, well within capacity for 200 psi pipe. Could use 260 psi for insurance. I did a calc to show that tensile strength of the pipe itself is no problem, but I wonder about those barbed fittings. I could have the supplier butt fuse fittings on the pipe to avoid the barbed fittings.

Oh, and I agree with the suggestion to pick a pump whose curve allows some water flow at lower water levels. Haven't decided on a pump yet.

What think about using poly at this depth?

 

[Craigpump]

Seems like a month ago there was a blog about the very same topic...

Anyway,

Stainless steel or brass male insert adapters are the least of my worrys. Years ago for the hell of it I put two insert adapters into short piece of 200 psi poly and pulled on it with my hoist truck. The pipe failed between the adapters failed while the adapters never moved.

The concern I have with poly being set with this low a static level are;
1) how are you going to control it? It may seem light now, but with a 40 pound pump and 100 pounds of wire along with no buoyancy, it will get heavy. FAST
2) how will you pull this out when the pump fails? Do you know someone with an up z dazy?
3) poly is very flexible and every time the pump starts it will whip around in the well, beating up the pump and wire

I would strongly suggest you have an experienced well/pump professional do this pump install with sch 80 or sch 120 PVC drop pipe.

Typical big brother beaureucrats, you must have a big tank but it doesn't have to be filled. How dumb is that?

 

[Reach4]

I suspect a 5 GPM 3/4 HP pump would whip half as much as a 10 GPM 1-1/2 HP pump.

 

[Odysseus99]

There is a logic to the large tank requirement. The fire dept can't defend your house in a wildfire if they don't have any water to do so. It's easy to require the tank when the house is built, but impossible to confirm that it is kept full of water. If someone has a tank and won't fill it, what can you do? You can't fix stupid.

I'm really trying to avoid using PVC in this well. The more research that gets done the more we are finding that the plasticizers in PVC are really bad. I don't want to use PVC drop pipe.

How much more expensive is using galvanized pipe for drop pipe than PVC?

 

[akcooper9]

The fire dept can't defend your house in a wildfire if they don't have any water to do so.

Thats why they passed the fire tax bill So glad we left CA for Texas.

As for the drop pipe, when I had my well done, I dont recall reading anything about pvc being bad for water and drinking from it.

 

[Craigpump]

Here in Ct, you can expect to pay 3 times more for galvanized pipe than PVC, then pay more for the handling of galvanized, plus galvanized doesn't have the same lifespan as PVC.

I've never had anyone ask about health concerns due to the use of PVC, but if I did, I suppose I would ask if they buy foods that are modified with hormones, drive a fossil fueled vehicle, had their well drilled with a fossil fuel powered machine, fly on commercial airliners etc.

In other words, it seems like everything we do can have a negative impact on something.