A couple of points;

1. if the old well is getting mud or whatever in it then the same stuff
will get into your new well unless the old well is properly abandoned.
You can get the procedures from your state groundwater agency. Most
states have laws about abandoning wells properly - a poorly abandoned
well can pollute an aquifer so you and your neigbours will all have
problems.You could spend all that money and be no further ahead and then
get into trouble with the state on top of everything. A good, registered
well driller should know all this and have included it in his quote but I
would bet he didn't include it or intend to do it. In my experience the
vast majority of well drillers are very poorly educated in their field.
In my area I've asked local engineers and government groundwater
specialists which driller they would recommend and they all said "none of
them, except maybe the one who is most expensive by far." He is most
expensive because he is the only one doing it right - the rest all are
busy but are getting by only on luck and the fact that consumers have too
much trouble suing them out of business. I don't think this situation
varies from state to state.

2. The whole issue of the pump has not addressed the basic hydraulics -
pumps are hardly ever installed near the bottom of a well. The pump needs
to be only deep enough that it has sufficient submergence at maximum
drawdown. Drawdown is how far the water in the well drops when the pump
has been running for a while. How long depends on the capacity of the
well and/or the groundwater formation. You could get some idea of this by
measuring the distance down to the water surface while the pump is
running - write down the measurement and the time, leave pump running for
another 10 minutes and re-measure, keep re-measuring every 10 minutes
until the level doesn't change. The flow should be at or better yet,
above the maximum flow you intend to draw from the well. You should
install the pump below this level plus a safety factor of about 10 or 20
feet. The safety factor ensures that the pump will never run dry so you
need to know if the groundwater levels change from year to year or season
to season and make sure the pump is below the lowest possible depth. That
is as low as you need to go and it should be no where near the bottom of
the well. There is a special well logging tape that has two wires in it
and a fitting on the end with two exposed contacts. When the contacts hit
water it beeps and you pull it up and down a bit until you know exactly
what measurement causes the beeping to start. Be careful not to get this
tape caught between the pitless adaptor and the well casing - took me
quite a while to get it loose. Alternatively, you can gamble that the new
well has exactly the same level as the old one and set the pump at the
same level in the new well. The well driller should do this pump test for
you before he leaves - don't pay him until he has done it.

3. Pump size depends on the lift from the water level in the well plus
all the hydraulic losses in the piping. It is most likely that the level
in the well will be the same as the old well and since ou are re-using
the old pump the flows and losses will not change. Therefore you can re-
use the old pump. You may get some improvement in pressure if you go up
one size in the pipe from the pump to the pitless adaptor.

4. Something I learned the hard way - wells can very easily get infected
by iron bacteria. Iron bacteria is everywhere on the ground. It gets into
wells by transfer from the well drilling equipment or from drill
equipment touching the ground and being put into the well. Even
installing the pump can infect the well because you have to lay out the
pump and pipe on the ground while you work. The driller is supposed to
disinfect all of his equipment between jobs but almost none of them do.
In addition, the driller is supposed to use chlorinated water for mixing
his drilling mud - smell the water truck for chlorine odor, if none add
enough Javex to get around 200 parts per million chlorine concentration.
When the job is done, pump installed, etc, add a jug of javex to the well
and leave it for at least an hour, 24 hours is best. Then run pump until
there is no more smell of chlorine. At a few dollars for the Javex, this
is cheap insurance to avoid a lot of future hassle.

5. The advice to get some professional advice was very good - take it or
be sorry. Most well troubles began while the well was being drilled or
planned. Try to be there while the driller is working, measure all drill
sizes, pipe sizes, pipe lengths, etc. Figure ou how to tell how deep the
drill is - there are marks on the rig and you can measure the length of
the drill rods. Then just count how many rods on the truck before he
starts aand then keep count of how many are down the hole and use the rig
mark to get a close part-rod measurement. If you don't track the depth
yourself there is no way to tell how deep the well really is or to sue of
you ever feel it was not drilled as deep as promised. The odds of getting
a 375 foot deep well if you are not there are slim to none but you will
sure get charged for 375 feet, probably more.

6. Well drillers are notorious for padding bills with extras - grouting
is supposed to be included but they'll try for an extra for cementing and
tell you it is something different - one is around the casing between it
qand the hole and the other is at the end of the casing. Don't fall for
it - both are art of drilling a well and should have been part of quote,
period. Then there is the famous "my bit broke and you as owner of the
well are responsible for it's cost, maybe $1,000, my guy tried for
$5,000. This is malarkey - he broke it not me. If the carpenter broke his
hammer I sure wouldn't replace it. When they try this one they usually
have put an old worn-out bit in the hole and are just getting a poor home
owner to buy them a new one. If you don't track the well depth during the
drilling you may get the old "we didn't get enough water at 375 feet so
we had to go deeper at $20 per foot".

7. The driller is supposed to develope the well when he is done - this
can mean a lot of different things depending on the type of rock drilled,
the type of well (cased, screened, etc). At a minimum he should pump out
at a rate of double your intended pump capacity for at least an hour.
This cleans out the well and proves that it can deliver the required
capacity. Capacity and drawdown are related so he has to take 10 minute
level measurements while he is pumping. All this info is supposed to be
recorded and one copy left with you and one sent to the state for their
records. It's a requirement of all wells drilled.

8. After you discuss all this with the driller you will get a revised
estimate to account for all your 'extra' requirements which he didn't
include in his original quote even though all of them are standard
requirements for all state groundwater agencies and thus shold have been
included unless he was planning a sub-standard job. Your final cost will
be closer to what another poster said he had experienced and his price
was half of what our only good driller charges.