Attached are some tables for matching a pump to a PEX circuit.
[Edit: Updated for more pipe lengths.]
Computations are done for equivalent pipe length circuits of 100 to 500 ft in 50 ft increments. Equivalent pipe length is the technique of converting elbows, tees, valves, and so forth to an equivalent length of pipe, so 125 feet of pipe plus a bunch of fittings might come out to something like 150 feet equivalent pipe length. Search online for more information on equivalent pipe length.
Circuit equivalent pipe lengths are round-trip, not one-way.
For each equivalent pipe length, PEX pipe of nominal diameters 0.75", 1.00", 1.25", and 1.50" are selected.
Then for each equivalent pipe lengh/PEX diameter combination, various pumps are selected.
For variable speed pumps two speeds are selected: max speed and minimum or close to minimum speed. Speeds are designated by suffix comprising a hyphen and Roman numerals. So if maximum speed is too much gpm and minimum speed is too little gpm then the pump will likely have a speed in between that is right for your application.
Constant speed pumps have no suffix.
Table columns are
fps=feet per second;
psi=psi pressure drop;
head=feet H20 pressure drop;
gpm=gpm;
watt=power estimate;
gpwh=gallons-per-watt-hour, which is a measure of relative efficiency. A bigger number is better, more flow with less electricity;
%gpm=percentage of maximum flow for that pump at that particular speed. Typically %gpm will be between %33 and %67 when the pump is well matched to the circuit.
pump=pump model
[Edit: Updated for more pipe lengths.]
Computations are done for equivalent pipe length circuits of 100 to 500 ft in 50 ft increments. Equivalent pipe length is the technique of converting elbows, tees, valves, and so forth to an equivalent length of pipe, so 125 feet of pipe plus a bunch of fittings might come out to something like 150 feet equivalent pipe length. Search online for more information on equivalent pipe length.
Circuit equivalent pipe lengths are round-trip, not one-way.
For each equivalent pipe length, PEX pipe of nominal diameters 0.75", 1.00", 1.25", and 1.50" are selected.
Then for each equivalent pipe lengh/PEX diameter combination, various pumps are selected.
For variable speed pumps two speeds are selected: max speed and minimum or close to minimum speed. Speeds are designated by suffix comprising a hyphen and Roman numerals. So if maximum speed is too much gpm and minimum speed is too little gpm then the pump will likely have a speed in between that is right for your application.
Constant speed pumps have no suffix.
Table columns are
fps=feet per second;
psi=psi pressure drop;
head=feet H20 pressure drop;
gpm=gpm;
watt=power estimate;
gpwh=gallons-per-watt-hour, which is a measure of relative efficiency. A bigger number is better, more flow with less electricity;
%gpm=percentage of maximum flow for that pump at that particular speed. Typically %gpm will be between %33 and %67 when the pump is well matched to the circuit.
pump=pump model
Last edited:
