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We've had unusually dry weather and our well has run so low that we had to call in a water hauling company to refill it a few days ago.

The water man told me that even though he dumped in ~ 1000 gallons, a great part of it will seep out of the well to the surrounding (drier) aquifer, the same way groundwater makes its way inside the well in normal conditions. Now a few days later, the water is low again.

I'm thinking some kind of drinking-water-safe plastic poly sheet sown or welded together at the seam would create a long and flexible tubing that could be progressively immersed inside of the well (with weight at the end) to effectively waterproof it on the inside.

The well could then be refilled to the top and hold all the water that it's containing, instead of slowly seeping it out. Under normal conditions, the sleeve can be removed.

The well is 2 feet wide, 15 feet deep. 2 ft diameter, 3 ft long concrete pipe sections stacked on top of each other.

There's also another well on the site (very low water as well) that's 4 feet wide, 15 feet deep - a much better candidate for the concept as it could hold twice as much water.

Does this sound doable? What are the problems I might face?

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  • $\begingroup$ I don't really have any experience with this sort of thing, but maybe you could use a material similar to Gore-Tex that allows water to pass through in one direction only. Then, water could seep into the well when the water table was high, but it would not seep out when the table is low. $\endgroup$
    – Carlton
    Commented Jun 24, 2015 at 0:12
  • $\begingroup$ Good idea, I did ask on the chemistry stack exchange if there was such a plastic available in sheet form. In the meantime I'm thinking 6 or 8 mil ldpe poly sheeting heat sealed to form the "tube" $\endgroup$
    – cannotcompute
    Commented Jun 24, 2015 at 1:25
  • $\begingroup$ I've NOT tried this :-) : To get a lined well to fill from seepage, with "not too much work" [TM] you could have a pipe from a sump in the well bottom that transfers water by siphon action into the liner. This could be started with a small submersible pump in the pipe that allowed free flow of water at lower rates (as typical magnetic driven pumps will). The siphon could be stopped as desired either by opening a valve at the top of the loop or by using the pump to suck water at a rate that lowered water at either end of the pipe to under the pipe end. | Harder to explain than to do, almost. $\endgroup$
    – Russell McMahon
    Commented Jun 25, 2015 at 11:15
  • $\begingroup$ Thought this is a fine engineering question in theory, you must be careful not to damage the water table by introducing materials that are hazardous, including those that can break down into hazardous components, or which can break down into nutrients. Product warnings are unlikely designed for the scenario you're asking about - such as typical marine specifications, which are for pools and watercraft $\endgroup$
    – New Alexandria
    Commented Sep 19, 2015 at 16:51

2 Answers 2

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I see two ways:

  1. I've had great experience in my pressure vessel design with a 2.3 mm thick liner of polypropylene or polyethylene. In a pinch, you can weld PVC, but I don't recommend it. Thinner stuff works as well, but the 2.3 mm allows you to place a weld bead on the edge using standard weld rod and plastic welding tools.

  2. If not, for a pretty reasonable DIY project, you can always coat the inside with resin, with a bit of fiberglass. (3 oz / sq ft of glass reinforcement should line it perfectly.) In terms of difficulty, think of putting 3 coats of wall paper on the inside of this well In the USA, drinking water approved containment services should be NSF listed. A great resin for coating the inside of the tank would be Reichold Dion 9102-00 Impact. It's NSF approved for coating any storage container or piping system.

By the way, all vinyl esters usually have BPA, if you're worried about that. Fortunately, they make FDA approved polyesters, which do not have BPA, but those aren't NSF approved.

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    $\begingroup$ The second option would permanently seal the well, I think the OP wanted something he could remove when the groundwater table is high so the well works again $\endgroup$
    – mart
    Commented Jun 24, 2015 at 7:49
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    $\begingroup$ True, but he could coat the top 14' with resin and the last foot could be a liner, with some strings for removal. $\endgroup$
    – Mark
    Commented Jun 24, 2015 at 10:43
  • $\begingroup$ #2 is NOT safe for a watertable or aquifer. Contaminating the water source of other people, let alone the ecosystem, just because is cheaper for you can place you in a position of legal liability. Well are registered, and your well can be sampled in the case of a contaminants investigation. no one should follow the design in #2. $\endgroup$
    – New Alexandria
    Commented Sep 19, 2015 at 16:55
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    $\begingroup$ All equipment designed to handle drinking water pass contamination investigation. That's the NSF 61 approval discussed for the Dion Impact resin listed. If you are curious, read the NSF certification for the resin for coating anything for storage of drinking water - it lists some minimum gal/in^2 specifications which the well falls into. Some people may take issue that BPA is not in the NSF contamination analysis to the levels that some studies recommend, but that's a legal discussion, not an engineering issue. $\endgroup$
    – Mark
    Commented Sep 19, 2015 at 21:34
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Well liners are generally made to order. One of your issues will be to find a company that can make what you want.

You will need to ensure the liner is the correct size and that it does not tear when inserted into the well, while being filled with water, or when it is being removed from the well.

You mention your wells are cased with concrete pipes. They will mostly be smooth on the inside of the well. However, there may be rough spots or chunks of concrete missing, or the joints may be rough and have sharp edges.

Every insertion and removal of the liner risks tearing or weakening the liner.

Another option, if the have the space, is to place a water tank on the surface and re-plumb the downpipes from all the roofs to discharge rain water (when it falls) into the tank. During droughts the tank can be fill by water brought in by a tanker.

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    $\begingroup$ I actually ran the custom liner by one of our estimators. A custom removable liner of 2.3mm thick material would run around $10 - 15k, depending on the material. The above ground tank would be a much cheaper option. $\endgroup$
    – Mark
    Commented Jun 24, 2015 at 14:03
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    $\begingroup$ If this is intended as a source for potable water, runoff from the roof probably won't be allowed to be mixed in, depending on the jurisdiction. $\endgroup$
    – Ethan48
    Commented Jun 24, 2015 at 15:14

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