Flow Rates of Water Softeners

The published flow rate of any of the water softeners we have on the web site are purposely underrated. For example; the Fleck 5600 metered water softener with 48,000 grain capacity shows a 12 gallon-per-minute (gpm) flow rate. Does this mean that 12 gpm is all you can expect to get out of this system? No. The published flow rate is the measured flow of water through the softener at a given temperature and pressure. In this case the inlet pressure was 55 psi and the temperature was 60F. If you were to increase pressure to the inlet, you can expect the flow rate to increase, in some cases by a great deal.

During one test we found that this same softener was able to produce a 14 gpm flow rate on 75 psi of pressure. That's not to say you'll have that kind of flow rate at your kitchen sink. The inlet pipe in this example was 3/4" copper. By the time your water gets to the kitchen sink, the piping size has decreased to 3/8" so the flow rate will be much less. We measured flow rate during this test right at the outlet of the softener.

When shopping for a softener the flow rate is an important decision making factor, but it is more important to select a softener based on the requirements of your water. It is not a good idea to purchase a system based solely on flow rate. If your water requirements call for a 32,000 grain system, then you should get a 32,000 grain system. If you select a much larger metered system, your softener will not regenerate frequently enough to prevent "channeling" of the resin media. You will also end up using more salt than needed.

Flow rates are affected by the diameter of the mineral tank and the internal size of the control valve, but it is the diameter of the resin tank that mostly influences the flow rate. The larger the diameter of tank, the higher flow rate results. For example; you have chosen a 32,000 grain capacity water softener to suit the needs of your water. With a 3/4" control valve (Fleck 5600, 2510 or Autotrol 255) you can expect between 7 and 8.5 gpm flow rates based on the control valve you choose. If you decide to go with a 1" control valve such as the Autotrol Performa, your system will be capable of 9 gpm flow rates. But take those same control valves and put them on a tank that has twice the resin capacity and you will be looking at flow rates from 12 to 13gpm for 3/4" valves and up to 14 gpm for the 1" valve. As you can see, it is the tank diameter that makes up most of the difference between flow rates.

Achieving higher than standard flow rates for smaller (9" diameter) tanks can be done to an extent with the high flow rate control valves out now. Commercial control valves such as the Fleck 2850 typically produce flow rates of 33 gpm, but to acheive that kind of flow, you would need to connect it to a 16" tank. The 2850 also requires a 1.5" connection. Fleck and Clack have come out with high flow control valves that are designed for higher flow rated homes. On a 9" mineral tank the Fleck 7000 can be expected to produce rates up to 13 gallons per minute on 1" pipe.

Flow Rate Increase?

I would be neglect not to mention a misconception that we keep running into here at Water Value based on phone calls that we get daily. If your home has a maximum flow rate of 7 gpm, purchasing a softener with a greater than 7 gpm flow rate will not increase the flow rating of your home. I know that seems obvious to most, but it is not so obvious to all.