Sediment and Sand Separation Strategies

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Zane Bridgers

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Hello,

About 5 years ago, we dropped our own 10gpm 2HP well pump 460' (thanks to the help of valveman and others on this forum) only to hit bottom before we could install the last 20' of drop pipe. Realizing we'd been shorted by the driller, we struggled to pull the pump back up about 10-15' before compromising and setting it. The well was tested at 18gpm, 360' static, feeding two houses.

Since then we have had variable amounts of sediment seasonally, and sometimes seemingly at random. It is especially bad when the well is run hard, clogging our 100 mesh spin-down filter to the point of losing water pressure. Sometimes there's as little as a 1/4 cup of sediment after a couple months, other times there's a full cup after just a few days of running lots of water. Here's what I've been considering...

Strategies:

1. ($$$) Hire a professional to life the pump another 10'
2. ($$) Install a Lakos SandMaster 10gpm unit upstream of the pressure tank for ~$600 - https://www.lakos.com/product/sandmaster-separators/
3. ($$) Install a water heater as a sedimentation tank before the pressure tank (steering away from this since I don't want all our drinking water going through a water heater long term)
4. ($) Install a 2" Rusco Spin-down Filter with no filter element before the pressure tank (I've heard they still work to drop out heavier sediment without the filter screen) - https://www.rusco.com/spin-down-and-sediment-trapper-filters

In all the above cases, I also plan to add an additional 60 mesh spin-down after the pressure tank and a couple 4.5x20" whole house sediment filters, 20 + 5 micron

I am looking for a lasting solution, but also plan to upgrade the pressure tank and switch, and would prefer not the break the bank on unnecessary equipment.

Thanks so much in advance! Hopefully this can help others down the line...
 

Bannerman

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You didn't specify, how the well was 'Developed'.

Proper initial development will eliminate much sediment and debris from the source.

One method to develop is to disconnect the drop pipe at the top of the well so as to allow the pump to pump out water with the least amount of restriction possible.

This will allow the existing pump's maximum velocity to carry the heavier sediment up the drop pipe with the water, and out from the open pipe, typically discharging into the field surrounding the well.

Well development may require continuous pumping for several hours to several days depending on the amount of time before the discharge becomes and remains consistently clear.

Since continuous pumping at high rate will usually result in a decrease of water within the well, this will typically increase the rate of flow entering the well from the surrounding aquifer, which will usually cause the smaller sediment particles surrounding the casing inlet screen to become dislodged and enter the well through the screen, so they will also be pumped to the surface. This will leave larger sediment particles that won't pass through the screen, to pack together on the outside of the screen, which will act as a filter to hold back any additional small particles from entering the well through the casing screen.

Another method of well development includes repeated 'surging' which involves pumping the water level lower and then adding additional water into the well to cause the water level to rapidly rise, to push the smaller sediment particles outward and away from the casing screen.

Some use an airlift method, using a large volume of compressed air delivered by a large diameter hose that is lowered to the bottom of the casing, to cause the water and sediment to be ejected turbulently out from the top of the casing.
 

Valveman

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I always recommend pumping out the well first. There is usually very little left to filter once you get the well cleaned out. Most people just don't like wasting water. But you have to waste a lot of water to get a well cleaned up. By pumping the well hard for hours, days, even weeks if needed, the sediment that will come out is pumped out. The sediment that doesn't come out sticks in the cracks and fissures and becomes a sand media filter to keep sediment out of the well itself.

There are lot of ways to develop a well. One thing I do not recommend is adding additional water to a well for any reason. Pushing the sediment back into the formation just means you have to deal with it again. Surging a well usually involves a surge black assembly in the well. When the surge block is pulled up it actually creates a suction below it that draws more sediment into the well, which is then bailed out.

Raising the pump in the well leaves a sump under the pump for sediment to fall into. If the pump will make 18 GPM as it is now, you should be able to raise the pump 20' or so, which should help with the sediment. Without a flow inducer on the pump, sediment can fill in around the motor causing a rat hole effect that will get the motor hot. Raising it may be the best option.
 

Zane Bridgers

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Thank you so much for the information.

As I recall, the well was developed using the compressed air method. He towed in some huge vintage air compressor and ran it for maybe a couple hours. Given the shoddy quality of some of the other work we observed, it would not surprise me in the least if this "development" was lackluster.

We filled up two 275 gallon totes with no flow restriction for the first few months before we had our household plumbing. There was definitely lots of sediment and mud at that stage. It has steadily lessened since, but still occasionally spikes as mentioned.

Our neighbor's well, about 100' away, is only 330' vs 460' and runs at 6gpm. It is 30+ years old and she still gets fine mica shist buildup in her filter, which needs cleaning every 1-2 months.

I do wonder if since we set our own pump, we missed that step. Perhaps he would have run the well hard for a few hours/days if he or a professional installer had set the pump.

Sounds like this spring we should have it lifted 20' and run it hard for a while. Can it be run for a couple hours at a time for several days or does it need to be continuous? In theory with a 10gpm pump and an 18gpm well we could run it indefinitely without much draw-down, but part of me still worries about running the pump dry and being in for an expensive replacement. Is this a reasonable concern?

Thanks so much for the help! By the way valveman, I've told many people about the csv valves since installing mine!
 
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