well production (posted by Linda)

[ASKNACHI]This question was posted on AskNACHI.org by Linda (from Cassville, Mo). [/ASKNACHI]About how many gallons per minute should an avg residential well produce?

An average flowrate of 10 GPM has been used as a conservative rate to ensure an adequate water supply by some residential well consultants. Southern Missouri wells have measured well over 100 GPM in some tests.

How deep is your well and what are you getting, now?

Linda,
When I do a well quantity check, I’m looking for 4.5 gallons per minute or better.
Mark

Linda,

You are wanting to know an “average” and not a “minumum”, is that correct?

What type, bored or drilled?

If you boys would pay attention, you would know the the original poster cannot answer your questions, as only NACHI members are permitted to reply to the original question.

Any additional responses from the OP would generate additional threads.

I agree with JB that 10 gpm is an adequate rate for a well supplying your average single family residence.

Linda

I agree with James and Jeffrey 10 - 15 gpm should be adequate for an average size single family residence. However if you’re in a large home with several bathrooms and / or lawn irrigation system or you’re thinking of adding an irrigation system this amount may not be adequate. An artesian well company that installs wells in your area should have that info.

alan

I wish there was some way to get clarification from the “asker”. There is a difference between the “average” that is produced and the minimum necessary to function. I’m wondering if we are hitting the mark with our responses.

Well’s do not produce water. Bored wells are just a resevoir, capacity is determined by bore size x depth of water. Drilled wells usually reach deep underground and tap into natural resevoirs or the aquafir. GPM is determined by pump type, size and supply piping. The amount of water needed daily depends on number of people, usage. In my area a 30’ bored well is guaranteed to hold 1000 gallons a day. They will bore up to 3 wells free until they reach the desired capacity. If the rock in your area is close to the surface, you will need a drilled well, as they cannot bore thru rock. Bored wells are charged by a set price, drilled wells are charged by the foot, but if you can afford it, drilled is the way to go. Hope this helps

I believe we are discussing “recovery-rate” Mr. Lott. Where the well is pumped at a fixed rate for a number of hours during which the level in the well is observed. Pumping is stopped abruptly and the water level is recorded as the water level rises in the well.

The “yield” of a well is dependant on many factors.

The minimum volume of water from a private well required for the issuance of a building permit varies from State to State and County to County. I would suggest that you contact your local county building department for information about your location.

The volume is not the only item important in determining an “adequate” supply, storage also enters the picture. A larger storage capacity can make up for low volume. Some counties set the minimum supply standards at
gallons per day", some have varying volumes depending on storage capacity.

In Stevens County Washington the requirement is only 800 gallons per day, which is twice the average daily family consumption of 400 gallons. With a large amount of storage this would probably be adequate, without the storage capacity in times of high use, the volume may not be able to keep up with demand. I’ve found that a combination of volume and storage that can provide 5 gallons per minute continuously for an hour or two, is adequate for almost any house hold situation, other than fire.

Here are some links that may help:

http://epa.gov/Region1/eco/drinkwater/pdfs/realtorprivatewell.pdf

http://www.des.state.nh.us/factsheets/ws/ws-1-8.htm

http://www.des.state.nh.us/factsheets/ws/ws-1-8.htm

Lewis asseeement is the most accurate. Ken’s not entirely correct, but does add to the conditions affecting yeild. A bored well is the mechanical equivalent of the older dug wells, but they go much deeper. When determining well yeild (which is what we are speaking of) a number of factors come into play, including static and draw-down rates, depth of well, hydrostatic head, and a host of other things.

As to yield, Lewis is correct that it varies from state to state and locale to locale. Typically, anything yeilding 5 GPM is adequate. 10 GPM is very good.

Low yield wells can be converted to 2-stage systems.

Shallow wells are more susceptable to contamination and to being run dry.

Hydrofracting can also help improve well yeild.

Finally, dont be confused by actual yield and functional flow. They are different. Mst HIs are measuring functional flow, which is what the homeowner experiences at the fixture.

Always look for a well drillers log. That is where the data on the well will be found, at the time it was constructed.

Joe, I appreciate and agree with your comments, but the original ASK NACHI Question was about gallons per minute, not how that figure was arrived at. All I was explaining was how the actual capacity or volume of the well was not the only factor in determining the amount of water available at the kitchen sink and what minimum volumes were required for a building permit for a residence.

A well producing only 1/2 gallon per minute into a sytem with enough storage could provide the residence with 5 gal per minute for two hours continuously each day. A well producing 5 gal/min with no storage could at times be hard pressed to keep up with shourt time demands.

Linda asked “How Much”, not how the volume was determined.

One of the problems I can see with ASK NACHI, is we, as inspectors, may get carried away when answering simple questions. The answer people seek may get buried in too “technical” of an answer. In this forum we should all remember the old rule of KISS.

Up here in my area of Ontario, Mortgage companies will want a minimum of 3 gallons per minute tested over 1 hour fwiw.

I think the ladies question was how many gpm at the faucet, so I was trying to help her out.

L,

You are correct, sir!

We have a old well and would like to know the production and quality