Artesian flowing well issues

[andyupnorth]

We have a new well and I just installed the pump equipment. The well is 330' deep artesian and the overflow is 2.5 GPM. When capped it builds up 6.5 PSI pressure. The submersible 7 GPM (correction - 10 GPM stated earlier) pump is hanging at 100' and the pitless adapter is installed at 5' below ground. The well drillers report indicates 25 GPM yield at 320' drawdown for 2 hours.
All is running fine BUT I'm not sure everything is the way it should be.

- In the top cap, I installed a vacuum release valve as shown in this picture: https://i.imgur.com/H6501Zu.jpg
- If I open a couple of hydrants at the same time the water level in the well casing sinks rapidly. When the hydrants are closed the water level rises again (without the top cap).
- When I have the top cap in place and open the hydrants I can hear the vacuum valve sucking air as the water level sinks.
- The water level is sinking in the casing running the 10 GPM pump. If the well yield is 25 GPM and the overflow is 2.5 GPM should the level go down if I take out 10 GPM?
- The well driller indicated 25 GPM yield at 320'. Is there any reason why he checked the capacity that deep?
- If I continue to draw water and the vacuum valve continue to bring in air, is it possible that I will fill the entire casing down to the pump with air and ruin the pump?
- If I remove the vacuum valve at the top and the cap is sealed, will there be a vacuum in the casing as the pump runs and how will that affect the pump and performance?

Any input appreciated.

 

[Reach4]

If I continue to draw water and the vacuum valve continue to bring in air, is it possible that I will fill the entire casing down to the pump with air and ruin the pump?

Interesting question. I suspect that would not happen, but if it could, how about a pressure relief valve up top? How about a valve that would let you measure the vacuum or pressure?

A question you did not ask is what would happen if there was no vacuum breaker? If a vacuum developed, I envision that just makes the pump see 30 ft less head (depending on barometric pressure) potentially. Maybe the vacuum breaker is to avoid having the pitless seal having to work against an increased differential.

And what about freezing?

I am not a pro.

 

[Sponsor]

 

[ThirdGenPump]

The wells yield is a nominal 25gpm at 320ft, it is lower at shallower depths, As you pull the water level down eventually it will reach a balance between outgoing and incoming water, assuming you are moving less than 25gpm. That would be the established pumping level for a given rate. It could be anywhere between 0 and 320ft.

The original yield was most likely established by air lifting out the water. They used the air compressor on the drill rig to blow all the water out of the well and calculated yield. It's not as accurate as pump testing the well but it's close enough for most projects. They tested at 320 rather than 330 so the bit was off the bottom.

 

[VAWellDriller]

I agree with everything said above.....the yield report could also mean that they encounter a 25 gpm zone at 320'...which is why they stopped at 330'. You should keep the vacuum breaker on the wellhead. If you didn't make any recommendations, and the well driller installed the pumping equipment he choose at the depth he choose..... I would run the hell out of everything now while it's new and under warranty.....I'm sure it's fine though.

 

[andyupnorth]

Yes, ThirdGenPump, the driller used air to make the yield test.

I installed the pump myself (not a pro). The equipment and height of the pump was the recommendation of the pump supplier based on our well report.

UPDATE;

Did some testing today. Replaced the pressure switch to a unit (still 40/60) with low-pressure shutoff function (~32 PSI). The idea is to protect the pump in case the air pocket will reach down to the pump.

What happened? Opening a couple of hydrants at full blast (taking out way more than 10 GPM.) Within 30 seconds the pump starts (below 40 PSI) and after 90 seconds the low-pressure switch kick off the pump (below 32 PSI).

The picture shows the setup:

The low pressure shut off might be caused by the dole valve (10 GPM) reducing the flow on the tank side while the hydrants are open lowering the pressure at the tank-T to below 32 PSI? Would I be better off placing the dole valve after the tank-T?

 

[andyupnorth]

Another test I did today;

Released the trapped air in the well casing by pressing down the vacuum valve until water came up.
Adjusted one hydrant to run at about 10 GPM.
The tank pressure was stable at 40-45 PSI.
The vacuum valve is still letting air into the casing (water level sinking).

Turned off the hydrant/pump after 12-15 minutes.
Released the air from the casing while timing the flow. After 18 minutes the air was gone and water up to the top of the casing.
Doing the math; 2.5 GPM flow x 18 min = 45 G. With 1.469 G/foot the air pocket reached about 30 feet deep.

What's going on? The well is producing less than 10 GPM since air is still entering through the vacuum valve?
If the well driller had a yield of 25 GPM at 320 foot depth would the result be that different at 100 foot?

 

[ThirdGenPump]

Yes the well produces less flow in the upper levels. In my area the general rule of thumb is you get 100% of the yield at 50% depth.

Mapping a well to know exactly what it produces at any given depth is an expensive time consuming process, this is typically too cost prohibitive to bother with on residential wells, an educated guess is almost always sufficient for determining depth and size of pump. To map that well I'd drop a 45gpm 5hp pump in on aluminum stick so I could throttle it to each given flow rate and measure the water level.

When in doubt it's cheap money to set it a little deeper. Once you have a pump in the well you can performance test it with that pump and determine what it produces in ranges that pump is capable of.

You have a well that can produce 25 gallons a minute all you need to do to ensure the pump never runs dry is install it below it's flow curve. The most a 1hp 10gpm can move from a depth of 200ft is about 15gpm. Set the pump at that depth and run it wide open for 4 hours. Then measure what it's producing. From that you can determine the pumping level at that flow rate based on the pumps performance chart. You can confirm performance by measuring the water level, I'd typically use a sonic measure but there are cheaper ways to go about it. A 10gpm pump can move about 18gpm unrestricted and drops as the water level pulls down.

No dole valve, no low pressure cut out. Those are safety features not needed for the yield of your well or the size of pumps you are using. Opening enough ports to allow more water than the pump can produce will trip out a low pressure cut out switch, the dole valve magnifies that effect because the pump can effectively produce less.

The board of health standards can vary town to town. We most frequently handle flowing wells by tapping an extra pitless that will allow the water to flow into the top of an underground chamber. Then that chamber has a drain to a pond or such. This creates an air gap so the well isn't contaminated. It also allows the well to vent normally at the top.

 

[Reach4]

The low pressure shut off might be caused by the dole valve (10 GPM) reducing the flow on the tank side while the hydrants are open lowering the pressure at the tank-T to below 32 PSI? Would I be better off placing the dole valve after the tank-T?

No. The Dole valve must be in line with the water from the pump to do its intended job -- to keep the pump from upthrust problems.

What is your precharge now? 38? You could see if dropping the air precharge to 36 helps. But not consuming more than what the pump can deliver is important. That 32? gallon pressure tank is smaller than you should have with a 10 gpm pump.

If you are concerned with the pump running dry, you might need something more sophisticated than a low pressure cutout. If your open valves are draining out more than 10 gpm, or more than what the pump can produce, then the low pressure cutoff could happen, even tho you are not out of water.

I don't know about your hard questions. Complex situation.

 

[VAWellDriller]

Another test I did today;

Released the trapped air in the well casing by pressing down the vacuum valve until water came up.
Adjusted one hydrant to run at about 10 GPM.
The tank pressure was stable at 40-45 PSI.
The vacuum valve is still letting air into the casing (water level sinking).

Turned off the hydrant/pump after 12-15 minutes.
Released the air from the casing while timing the flow. After 18 minutes the air was gone and water up to the top of the casing.
Doing the math; 2.5 GPM flow x 18 min = 45 G. With 1.469 G/foot the air pocket reached about 30 feet deep.

What's going on? The well is producing less than 10 GPM since air is still entering through the vacuum valve?
If the well driller had a yield of 25 GPM at 320 foot depth would the result be that different at 100 foot?

What's going on is the water level hadn't stabilized yet....sometimes it takes hours and you only ran the well 12-15 minutes. Usually most of the drawdown occurs in the first few minutes and you figured the water level had dropped 30'....which showing how you figured that seems to be reasonable. You should do the same test and run it wide open for hours if possible if that will make you feel better. I think more than likely you have a good setup...good pump at good depth and there is no reason at all for a sole valve or low pressure cutout switch. If you're really worried about it you need to run it for an extended period at the highest rate you can....put the hose(s) down in a bucket you will see air bubbles if the water level ever goes that low.

 

[andyupnorth]

That 32? gallon pressure tank is smaller than you should have with a 10 gpm pump.

The tank is 81 gallons. Should be sufficient (I think).

 

[andyupnorth]

Thanks for all he feedback and explanations. Highly appreciated for a newbie like me...

I think more than likely you have a good setup...good pump at good depth and there is no reason at all for a sole valve or low pressure cutout switch. If you're really worried about it you need to run it for an extended period at the highest rate you can....put the hose(s) down in a bucket you will see air bubbles if the water level ever goes that low.

....so you suggest remove the low-pressure cutout switch and the dole valve and run it for a few hours to let it settle? Wouldnt that "over-speed" the 10 GPM pump (due to the upthrust) and potentially ruin the pump bearings?

 

[ThirdGenPump]

....so you suggest remove the low-pressure cutout switch and the dole valve and run it for a few hours to let it settle? Wouldnt that "over-speed" the 10 GPM pump (due to the upthrust) and potentially ruin the pump bearings?

That could be a concern after 20 or 30 years. ON smaller pumps upthrust is of minimal concern. The motors usually fail before the bearings wear out on the wet ends. If you are using a plastic cast pump it's of greater concern but you'll be replacing that in 8 or 9 years regardless.

 

[andyupnorth]

The board of health standards can vary town to town. We most frequently handle flowing wells by tapping an extra pitless that will allow the water to flow into the top of an underground chamber. Then that chamber has a drain to a pond or such. This creates an air gap so the well isn't contaminated. It also allows the well to vent normally at the top.

This is not an option. The state doesn't allow any overflow for any reason. Spoke to the water resources inspector about this since it was often done in the "old days" (or when the inspector looked another way )

 

[andyupnorth]

ANOTHER UPDATE
did additional tests today trying to understand what's going on;

- Removed the 10GPM Dole valve.
- Replaced the pressure switch to one w/o the low pressure shut off. (Correction: stated 10GPM pump earlier - it's actually a 7GPM pump).
- Opened one hydrant at full blast - 11GPM for 30 minutes (after depleting the air pocket in the well casing).

After 1/2 hour the outflow from the hydrant: ~330G. Then depleted the air in the well casing (venting the vacuum valve). It took 24 minutes for the water to reach the top. If the well overflow is still 2.5GPM the air pocket would have been down to 40' (or 60G). With the water volume in the casing (60G) and the well overflow during the 24 minutes (60G) the overflow and the volume of the casing adds up to 120G while I took out 330G.

Does it mean that the well produced 210G? (330G-60G-60G). That would be 3.5GPM. Does it sound right?

The suggestions earlier were to run the well pump for four hours - just afraid to do so for the risk of ruining the pump.

 

[Valveman]

I have a well pump that hasn't shut off in 18 years. Running is what pumps are made to do. They can run 24/7/365 without any problem, as long as you don't pump the well dry. You are testing the recovery rate of the well to static, not how much the well can produce. If the water level only pulled down 40' the well will make more than 3.5 GPM. The well report says the well will produce 25 GPM at 320'. So that is what you would have to do to test the well properly. With so much stored water in the well and because it is recovering so quickly, I don't think any of this is important. If you need more water, just set the pump deeper than 100'. If you set it at 320', you would have 25 GPM available if you need it.