artesian well needs chlorinating

[Qwertyjjj]

artesian well needs chlorinating
We have an artesian well that faile dit's water test for coliform bacteria (we've been drinking it and no problems

)
The well has been there for 30+ years so no idea how deep it is.
The cap seems to be bolted on - can I just undo the cap or will pressure force some of the water out? There is a pump attached to it that I assume pumps up the water to the house.
I need to measure the depth with a string and fishing weight so I can throw some chlorine in - any ideas on how to proceed?
Tere are 2 abandoned wells within about 50ft of the well so am hoping they are not contaminating it. The water has also smelt of sulfur for a long time but that seems to be a common problem in the area so I don't think it's sulfur bacteria.

Will the well cap be under pressure?

 

[Valveman]

If this is a true artesian well the water will flow out the top, but there should be very little if any pressure. If the water is flowing out when you remove the cap, it will be hard to get chlorine to go down where it needs to go. You really need water to flow back down the well so the chlorine gets forced out into the water formation to get to where the problem is.

Some artesian wells do not flow, and you should be able to get chlorine down where it is needed. You really need to chase the chlorine with enough water to force it out the bottom of the well where it is needed.

Yes a couple of open holes close to the well could be the source of contamination. Anytime rainwater can run down a well it takes everything that is on the ground down with it. Dog crap, fertilizer, pesticides, etc., can be getting in your well. I would properly seal all open holes in the areas before even trying to chlorinate the well.

 

[Sponsor]

 

[Craigpump]

Well first off, forget the string and fishing weight. More often than not the string gets wrapped around the pipe and through the wire and either doesn't get to the bottom or you won't get it out. Plus, you need a pretty good sized weight in order to feel the bottom of the well.

A better idea is contact the local health and or building dept and ask for a completion report on the well.

The well should come right off after loosening the bolts.

You should use chlorine designed specifically for water wells. There are a few posts about how to properly chlorinate a well here on the site.

I would put chlorine in those two abandoned wells also.

 

[Qwertyjjj]

If this is a true artesian well the water will flow out the top, but there should be very little if any pressure. If the water is flowing out when you remove the cap, it will be hard to get chlorine to go down where it needs to go. You really need water to flow back down the well so the chlorine gets forced out into the water formation to get to where the problem is.

Some artesian wells do not flow, and you should be able to get chlorine down where it is needed. You really need to chase the chlorine with enough water to force it out the bottom of the well where it is needed.

Yes a couple of open holes close to the well could be the source of contamination. Anytime rainwater can run down a well it takes everything that is on the ground down with it. Dog crap, fertilizer, pesticides, etc., can be getting in your well. I would properly seal all open holes in the areas before even trying to chlorinate the well.

Thanks.
Of the other wells are contaminated I don't really understand how contaminated water could get into the new well. If it's all filtered just like rain water then how could coliform in tank b 50ft away get into tank a? Surely there's cilifirm on the grass above tank a anyway?!

Local health department has no record.

 

[Valveman]

Your pumping from a well not a tank. Most wells get water from an aquifer, which is kind of like an underground lake or river. Whatever goes in upstream can be in the drinking water downstream.