Question
I installed a 12 zone sprinkler/irrigation system over 7 years ago on our 1 acre lot.  It has been supplied by the same 110v, 1hp pump that supplies the house.  I want to install a 220v. 1.5hp pump just for the sprinkler system.  The current pump is part of a sealed pressurized setup for the house.  I don't want to use a pressure tank with the new sprinkler system.  As it is now, different zones put slightly different loads on the pump.  Some zones just about keep the pump running constantly while others have it cycling off for long periods.  Nearly all zones use the smaller nozzles at each head but I plan to try to balance out the new supply and demand for each zone by adding heads or changing the nozzles.  However, there may be situations that I cannot increase demand enough to match the new pump.  Will I have to have a pressure switch on the pump or are there other ways to keep the pump running without building up pressure while supplying the smaller zones?  What recommendations can you give?  Do I have to go with a pressure tank and switch?

Answer
Hi Sandy

Unless you want to incur the substantially greater expense of a VFD pump and module, I cannot think of another solution than a separate pressure tank and switch with a differential setting as far apart as possible.

Variable Frequency Drives are typically found as part of larger pumping stations where there is a large difference in pressure required and a conventional switch & tank combination is impractical. They are available on a smaller scale but are typically out of most home-owners budget range.  A VFD assembly adjusts the speed of the impeller based on the demand of the system providing only enough power to the pump to supply the water called for.  As the demand changes, the module regulates the motor, in turn regulating the output of the pump.

It may be worth investigating if for nothing else, a bit of background on this emerging technology.

Good Luck,

Tony