Drawdown issue under Drought conditions? Or something else?


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Old 06-06-11, 03:45 PM
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Drawdown issue under Drought conditions? Or something else?

We are having a repeat of an issue we experience two years ago during drought in Texas. Just two of us live here. New, high efficiency washing machine and dishwasher, both run no more than twice a week. Other than a little water use at the sinks, and flushing toilets the only other water we use are nightly showers.

We are trying to at least maintain the grass immediately around the house. I use one small sprinkler that puts out, at most, a ten foot diameter circle. In no more than half an hour I can look out the window and see water barely coming out of the sprinkler, at which time we might get only a trickle out of a sink. I'll turn the sprinkler off at that point. Water pressure rebuilds fairly quickly. At no time do we ever get air through the pipes when the pressure drops off so the pump is not sucking air.

From my research it looks like there are a couple of possibilities.

1) The static water level is low due to the drought and may be just barely above the submerged pump. Drilling Logs from the 1984 install show static level at 147 with 196 feet of pipe. The log does not indicate placement level of the pump. Would it be safe to assume that it was placed about halfway between static water level and bottom of the pipe? The pump was replaced about three and a half years ago. I don't know if the well guy took a new measure of the water table at that time, before he set the new pump. Surely he did, right?

2) The intake 'grill' could be gunked up with foreign matter (sand, etc) and reducing the intake of water. How is that fixed? Blow it out somehow?''

3) I read somewhere (but can't find it now) about sediment building up in the 'reservoir' down there and it can be blown out, making the reservoir larger again.
It would be hard to believe that this is an issue unless the pump is sitting near the bottom of the well.

4) A tank issue? Well-X-Trol WX252 86 gallon capacity. I just went out and timed the pump. Switches are set 40/60. With a shower and bathroom faucet open and running it took 1:43 minutes until the pump shut off. With all faucets closed off (no water running) It took 1:10 minutes for pump to shut off. I then drained the tank. I turned off the pump, opened several faucets, tubs in the house until water stopped. Closed all the valves. Tire gauge measured about 17 pounds! I brought it back up to 37/38. Turned the pump power back on. It now took two minutes and four seconds to full a completely empty tank.
Does any of that mean anything to you guys? Good or bad?

I have a call in to my well guy. He and his dad have been doing this county for about 50 years. Probably 75% of all wells. Extremely trustworthy.
It would be great to get some suggestions and ideas before he calls.

Thanks!

Ken
 
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Old 06-06-11, 04:28 PM
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More Information: So, after I brought up the air in the tank I decided to see it made any difference in our problem. Looks like it did not. I turned the little sprinkler on. After about half an hour I checked it and saw that very little water was coming out, but after about ten seconds the pressure built up and it ran normally for maybe 30 seconds, then fell off again. Did this cycle a few times. I went to tank closet and noticed that the pressure gauge was down to about 15psi. After a few seconds it built rapidly to 40 but stopped right at 40. Held there a few seconds, dropped like a rock down to 15 again, then rebuilt to exactly 40. I watched this cycle a few times then turned off the sprinkler. After I turned the sprinkler off I went back to the tank. The pressure was now up to about 50. It slowly built up to 60 then shut off. As the tank was refilling, it sounded like there was a rush of water for several seconds, then it slowed down to a trickle for maybe 15 seconds, then another sudden rush until it hit 60psi.
I'm certainly a novice but this seems more and more to me like a drawdown problem - caused by a lowering of the static water level. If this is the case, what would you pros do? Lower the pump, blow out the intake, both?
About how much lower would you go? Would five or ten feet be sufficient?
 
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Old 06-06-11, 04:42 PM
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Sounds like all is working, and you did everything correct. That sprinkler wants more gpm then the pump can produce. Do a bucket test to see how many gpm you can produce.

Fill a 5 gallon bucket from a hose bib.

300 divided by the seconds it takes to fill a 5 gallon bucket = GPM

I think submersible pump should at least 10 gpm. My shallow well pump only does 5-6 gpm. I run One - 4 gpm sprinkler at a time.

Do the bucket test and let us know.

Mike NJ
 
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Old 06-06-11, 05:02 PM
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Mike, I ran out and did as you suggested and came up with exactly 10GPM. (took exactly 30 seconds to fill the bucket)
The sprinkler is just a little bitty thing. My neighbor, whose well is about 150 yards away and is a totally different water table (static level 78. pump 123. well depth: 137) runs two or three sprinklers all day long, nearly every day, and never has a pressure drop.

Okay, so it looks like our pressure is good. Tank and pump performing okay. Would it not do any good to lower the pump head?

Do oscillating sprinklers pump less water?
 
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Old 06-06-11, 05:14 PM
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What part of Tx are you in? Just got back from a water well meeting and there are definitely a lot of wells all over the place drying up, although we do not have that problem in this county. Although your pump can pump 10 gpm, it obviously cannot sustain it. Let it pump for awhile, 20-30 minutes, and then measure the output. It seems obvious that your pump is over-running your well.
 
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Old 06-06-11, 05:25 PM
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I'm in Austin County, near Bellville. When I ran my test a little while ago it had been about an hour since I had turned the sprinkler off and no water had been running anywhere else in the meantime. Are you suggesting I run the sprinkler for 20-30 minutes and THEN do the bucket test again?

For what it's worth...I just checked the receipt for the pump install. It's a Goulds 10GS. One horse. 10gph.

So, by over-running, I assume you mean I'm pulling out water quicker than it can recharge? In that situation, is it worth lowering the pump? (If I'm getting 10gph it's not likely that the screens are clogged.) Since this happens only in drought conditions, the recharge rate in relation to the level of the pump seems to be the issue. I'd just like to know if lowering the pump is the way to go. If so, by how much, and what the costs might be.
Thanks.
 
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Old 06-06-11, 08:34 PM
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I talked to our well guy tonight. He said a lot of wells in this area are going dry. I gave him my test numbers and the times it takes to hit max pressure once the pump turns on, etc. He said the pump is working just fine and the tank seems to be in good shape. He agrees that the sprinkler must be drawing too much for the current static level but he thinks the pump is probably already as low as it should go. He doesn't have a record of the pump depth but if the original static lever was 147 and the pipe depth is 198, the said he probably put the pump about 180. Guess it wouldn't be a good idea to put it too close to the bottom. He also said he was surprised that, since we seemed to be over drawing the well, that we are not sucking air.
So, since we never have pressure problems in the house, which is the priority, we'll have to live with only being able to water for short periods at a time, at lease until the water level gets so low we can't service the house anymore, then we'll have to talk about a new well, or hooking back up to the community water system.

I'd still like to hear the opinion of you folks on the board.

Thanks,
Ken
 
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Old 06-06-11, 09:49 PM
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I say its the sprinkler.... If your drawing down the water below the pump its either water, no water, or spurts of water and air. I am not understanding the other posts of the pump going from say 10 gpm to say 5 gpm. Once you draw the cone below the pump you should draw air. Its like sucking water out of a fully saturated sponge. You get all water. Now try sucking the same amount out of a semi wet sponge.





How are running the sprinkler? What pipe or hose? Size? Any leaks in the hose? How many GPM is the sprinkler, and what type? Is it new or did you always have it? Has anything changed.

Pull your aerators at the sinks. Any sediment?

Mike NJ
 
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Old 06-06-11, 10:04 PM
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Had the same problem with the same sprinklers two summers ago. We have two of them but only ever run one at a time because of this issue. There are just little round, metal donut shaped things with lots of holes in them. They don't oscillate or move at all. I don't even usually turn the faucet on more than half way. They just sit there and throw out, at most, a ten foot diameter circle of water. I'm going to take one tomorrow and stick it in that five gallon bucket and time how long it takes to fill the bucket, so I can get a flow rate. Half inch hose. I buy heavy duty hose. No leaks in hose or connections. Maybe this type of sprinkler is high flow. I've got several pulsating sprinklers that are suppose to be low pressure sprinklers (I just read that!) So, I'm going to test those out tomorrow.
Sediment in the aerators? I just checked three sinks. No sign of sediment.
Again, though, even when the water pressure drops off to almost nil, we've never had air gushing out of the pipes.
 
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Old 06-06-11, 10:25 PM
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I'm going to take one tomorrow and stick it in that five gallon bucket and time how long it takes to fill the bucket, so I can get a flow rate.
I was just going to suggest that. Where did you get the sprinkler? Brand? Sometimes they have the GPM on them.

Or just put pulsating on and try it. My pulsator is about 4 gpm. If yours say for low pressure it just got a restrictor in it.

Mike NJ
 
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Old 06-07-11, 10:53 AM
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That's actually 10 GPM, not 10 GPH. That pump, or any other submersible pump, will never "suck air". It will lose all flow and sometimes become air locked, but it will never pump any air to your tank. It's also, IMO, a very high quality pump and should last you a long time. It's really bad for you to run the water until the pump can no longer produce enough volume to sustain the system. What you're doing is running the risk of running the pump dry, which in submersible pumps is a big no-no.

My advice is to use soaker hoses at very low flow, or pray for rain. Good luck.
 
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Old 06-07-11, 12:04 PM
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Been praying for rain for a loonnggg time! I'm going to do a bucket test on different sprinklers.

Wellman... another question. What are your thoughts on wells being naturally recharged? If my static level was 147 feet when the well was put in in 1984 (and who knows how low it is now) can I really expect rainfall to ever make it through 150 feet or so of sand and clay and replenish my reservoir? I can see if someone tapped into a confined system between two solid rock layers, that rain water might make it's way through cracks in rocks and recharge that.
I just can't see ever getting enough rain to refill what was probably "fossil" water in the first place. I expect that one day we'll have to drill a new well.

Is there a simple way for a layman to figure out his current water level without a lot of fancy tools. Or should I not mess with it. I'm certainly intrigued.
 
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Old 06-08-11, 11:55 AM
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I'm certainly not a geologist, but I will try to answer the question to the best of my knowledge.

The water you are using right now is water that entered the ground hundreds, if not thousands, of years ago. Part of the water that comes down as rain today enters the ground, and slowly makes it's way through the "impermeable" layers of rock, soil, and clay. As the water percolates down, it is naturally filtered by the layers of sediment, and it also picks up natural minerals that give it hardness etc.

The static water level in your well only has to do with the amount of pressure that the water has at the aquifer level. The more water in the aquifer, the more pressure. Also some aquifers stretch for hundreds of miles, so the water you are drinking and using could have entered the ground far away from where you are using it.

My answer is that the rain we get today, tomorrow, yesterday, and even last week doesn't have any direct effect on recharging your aquifer. What it does have an effect on is how much water is being pulled from the aquifer. Less rain, more water being used from groundwater sources, so that is why the level goes down when there is a drought.

It should be noted that there are places where the rainwater does have an immediate effect on the groundwater recharge levels, it all has to do with how the aquifer or formation is formed. Confined, unconfined. I'm not that educated on it, but there are resources out on the web like the USGS.

There are several ways to measure the static water level of your well, but the most direct one is to open end your pump and see how long it takes it to drop off or how much it drops down too. As the water level recedes, the pump flow will decrease. If you know your pump setting depth you can make a rough calculation on the static water level. I have a pump set at 180 that will completely run dry (low yield well).

I am betting that your well is producing slightly less than the pump can pump. That's why it takes an hour or so to see the effect. 4" casing holds about .6 gallons per foot, so you have a good amount of water in the casing before you start to see the effects.
 
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Old 06-08-11, 12:06 PM
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aquifer map

 
 

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