See
https://www.shop-esp.com/NuWell100.aspx "How to use".
It does not say don't cap, but it doesn't say to cap. It does say that you may want to add water. So I am thinking they are thinking no cap or loose cap to keep debris out.
It does say " Agitation of the acid into the blocked area will greatly enhance cleaning."
I guess agitation could be done in more than one way. Maybe a capped PVC pipe could be moved up and down as a plunger. Three sticks of 3/4 glued together with 2 couplers and a cap on the end could do it. One-inch PVC should fit too. The cap would be about 1-19/32 wide. Let the glue harden before using. You would not want it coming apart.
They don't get into the adding of water to chase the acid through the screen into the aquifer. I think that is an important part of the process. I think I would let it sit with the pellets dissolving, and add water more than once. As I picture it, the exhausted acid would be replaced with fresh acid. So I am thinking overnight after letting the pellets fall to the bottom, and adding 1 gallon of water. The next day I might add 1/2 gallon at a time with maybe an hour between. I have never done it. my 1/2 gallon per hour is just a guess as to a reasonable rate. I hope somebody has a better prescription.
A professional well driller would not have the time to do it economically that way, but it would be easy for you.
