I was wondering what is the acceptable value (GPM) for wells.
Assuming the psi is between 40 - 60 psi. Is the a rule of thumb for wells for flow? And what is the correct procedure for testing a well?
Thanks
Frank
4 - 8 GPM
Use a hose at the hose bib closest to the interior tank. A 5 gal bucket, and a stop watch (or watch with a second hand).
Let the water run for about 15 minutes, then check it for 30 seconds or so. Re-check every 15 min for an hour. They should all be about the same.
Keep an eye on it though, if it starts to run cloudy or brown, shut it down. If there is sediment in the pump you can burn it up.
They also make flow meters if you want to go a little more hi-tech. There’s some other things that also need to be done if you are inspecting a well, but that’s how you check the GPM.
I use a flow meter instead of a bucket. But either work.
New Hampshire actually published a recommended (not required) standard to evaluate the flow from a private well.
minimal - 5 gpm for 2 hours. (600 gals once per day)
optimal - 4 gpm for 4 hours (960 gals once per day)
Here’s a link to their well recommendations
Nick,
That’s old school.
I test the pressure. Later, I run the shower and flush the toilet. If the shower doesn’t diminish, it’s OK. It’s called testing “functional flow” and that’s all that my state requires that I do.
I hope no one runs all that water into a septic system. Septic systems are designed for normal use, not flooding.
Beyond the scope of a home inspection.
“The water supply is private and provided by a well, which is the sole responsibility of the homeowner. The source of the water could be from a local spring or a more substantial aquifer, which are dependent upon rainfall. For this reason, neither the supply nor the quality of the water can be categorically guaranteed. Also, you should be aware that local and regional standards of adequate flow vary considerably, but are entirely dependent upon the yield of the well and are best determined by a specialist.”
Bruce King writes:
The www.nachi.org/well-meter.htm solves this problem. Unlike a meter that hooks to a laundry tub and drains all the water into the septic… our well meter has an output that permits you to attach a garden hose to run the water into the yard or down the driveway or whatever.
If I’m doing a well flow test I typically use a hose on the external bib. Around hear a 100 ft hose has always been able to reach a decent discharge point. (Away from house and draining away).
What I’d really like to have is a flow meter with either a warning signal or auto cutoff if the flow drops below some present point to avoid running the well dry. Lacking that you want to check the flow frequently. If it drops below the minimum I end the test and say it did not meet the criteria.
On trick I have learned doing these is if you are using a flow meter be sure to dial it down so the flow just meets the rate you’re testing. Some wells can put out very high flows that can outpace the recharge rate of the well. But if throttled back to 4 gpm( 4 hour test) or 5 gpm (2 hour test) will run all day without problem.
That’s one reason for using a flow meter instead of a bucket as it’s just easier to dial back the flow rate accurately. You can do it with a bucket but then you have to time the filling of the bucket.
if the well runs dry before you finish your inspection…you will either need to write it up or find another job that you’re faster at! 