Unusual Parameters and Needs
"I only have a little water in my well. What do you recommend?"
The difference of just ten feet between your static water level and the bottom of your well is unusually small. It leaves a very small buffer of water to pump that would be quickly exhausted if you had a modest recovery rate. (The recovery rate is the speed at which the well refills after pumping.)
Because there is so little margin of error for this well, it would be prudent to make very sure about the water level and depth.
You should also ask the person who drilled your well what the recovery rate is. With a recovery rate significantly higher than 3 GPM (which is the capacity of our of our smaller 100L pump), installing that model in your well would be workable, even with that very small buffer.
If that is not viable, another option is to drill the well deeper, at least 30 more feet.
Speaking with the driller, or someone else who understands your well, is critical to answer another question: Does the water level fluctuate significantly throughout the year? If the static water level is (as you say) 90 feet, but at the driest part of the year is 100, then you do not have a viable well at all, without further drilling.
"Pumphouse ceiling lower than length of drop pipes."
“The drop pipe lengths are 9 feet but the roof to where my well is is shorter than that. Are the pipes flexible enough to bend a little? The roof is about 8 feet."
No. The drop pipes are not flexible enough. Schedule 80 PVC tubing has very thick walls relative to the diameter of the tube. You will need to buy half-length drop pipes.
"I have a Buried Tank."
“I have a 550 gallon tank buried underground, not a well, would I be able to use your pump for this type of installation?”
Yes. You would be able to use our pump for this type of installation.
To make our pump work with an underground tank, it needs to anchor to a (cylindrical) well casing (2, 4, 5, 6, 7 or 8 inches diameter). Specifically, the pump head is attached to the cap, and the cap is affixed to a casing.
The well casing must be vertical from top (ground level) to tank, terminating at the top of the tank, or within it. The series of lift rods connecting the top (pump head) to the bottom (pump cylinder) would extend into the tank, terminating very near its bottom, and ending with the pump cylinder.
"For a 7" casing diameter."
7" water well casings are very unusual, but they do exist. Here's what you need to know to make sure the diameter is accurate.
The water well industry standard is to specify diameter using INSIDE DIAMETER (ID). So, in your case, if you have a standard 7" pipe, the inner diameter (ID, measured from the inside edges of the pipe, viewed in cross section) would be 7". The outer diameter (OD, measured from outside edges of the pipe, in cross section) would be 7 5/8 (7.625) inches.
"I have a low recovery rate."
You could draw down the water and end up sucking air. Pumping air for any length of time can void our five-year warranty. When pumping air, after the seals wear down (which doesn't take an awful long time, when dry). In the extreme, the piston could even start scratching the precision-machined pump cylinder. Not good.
For a well with a low recovery rate but with a tall column of water, the best remedy is to locate the Simple Pump further than usual below the water's surface.
Very Little Water in Well AND Low Recovery Rate
Let's consider a possible example of a 1 gpm recovery rate, with only 5 feet of available water, and a 4" casing size. At about 2/3 gallon per linear foot, the buffer is around 3.33 gallons.
Even our lower-capacity 100L will quickly exhaust this buffer. Pumping at capacity, you will exhaust the available buffer in just over a minute. Then you'd wait 3-1/3 minutes for the well to fill back up. Then pump for one minute. And so on. Not really viable.
For such a marginal well, the only real option is to deepen the well.