If your static level is 90’ and you set the pump at 160’ you have a minimum of 105 gallons stored in the well. Since the recovery rate is 7 GPM, with the 105 gallons stored in the well you could use 10 GPM for 35 minutes before the well is down to 7 GPM. I doubt that even two houses will use 10 GPM for 35 minutes straight. If you run sprinklers or any other long term uses of water, just use less than 7 GPM at a time and you won’t run out of water.
An 80 gallon pressure tank only holds about 25 gallons of water. Larger or extra pressure tanks by themselves don’t help with low producing wells. They are actually seen as an additional load, which can make things worse. You have just as good a chance of a big pressure tank being almost empty as you do of it being almost full when you start to use water. Either way the pump has to refill the 25 gallons in the tank at the same time it is supplying water to the house. So water stored in a pressure tank has to be replenished by water from the well, which is what you don’t have much of.
When the tank is almost empty and you start using water, all you have is what is stored in the well plus the 7 GPM replenish rate. Then even when you stop using water, the tank will need to be refilled before the pump will shut off. With the well pumped down you have 7 GPM, and the pump is trying to refill the pressure tank at 10 GPM. So the extra load of a big pressure tank causes the well to be pumped dry. Then something like a Cycle Sensor will be needed to shut the pump off before it is damaged. Now you are out of water until the well refills.
A Cycle Stop Valve will let any size tank refill at only 1 GPM. So your well would be refilling at 6 GPM while the CSV is refilling the tank at 1 GPM. You have a 50/50 chance of a large pressure tank being almost full when you need water, which would give you an extra 25 gallons before the pump even starts. With the CSV refilling the tank at 1 GPM after you stop using water, the well won’t be pumped dry while refilling the pressure tank. However, when you use 25 gallons out of a pressure tank before the pump starts, the pump has to put the 25 gallons back in the pressure tank before the pump will shut off. The only useful stored water you have is in the well, not the pressure tank. So it really doesn’t matter, and can actually be better to have a pressure tank that only holds 1 gallon of water.
If you need more water than is stored in the well, a storage tank and booster pump is needed. You can always add a storage tank and booster pump or drill another well later if the well has any problems keeping up with 2 houses.
Centrifugal and Jet Pumps have the same type of centrifugal impellers as submersible pumps. They will reduce in amp draw when restricted by a CSV the same way most submersible pumps will. Saying a CSV will extend the run time and therefore increase the energy consumption is not true. It depends on the amount of water you are using at the time. If you are using between 70% and 90% of the pumps max flow, a CSV will reduce the rapid cycling enough to actually decrease energy consumption. The CSV may increase energy use slightly when using less than 70% of the pumps max flow. However, reduced cycling makes the pump system last longer, and along with the reduced cost of a smaller pressure tank, the CSV more than offsets any possible increase in energy consumption. Anyone who has experienced a shower with a constant 50 PSI, would never valve off a CSV for any reason and go back to seeing the pressure in the shower bounce up and down from 40 to 60 PSI.
