WaterGroup WG185ACF75, Owner'S Manual

Sizing Requirements 

Water Pressure 

The water system must have a pump big enough to deliver the recommended backwash 

rate with a minimum pressure at the inlet of the filter of 30 psi. If the existing system can-
not do this, it must be upgraded to do so. Whenever possible, the water system should be 

adjusted to deliver at least 30 psi for even more satisfactory results. 

Backwash Flow Rates 

The most important criteria in sizing a filter is the capacity of the pump. The water must 

pass through the filter media at the proper service flow rate.  The filter must also be back-
washed at a flow rate sufficient to dislodge and remove the captured particles.  Failure to 

provide sufficient water will cause a build-up of particles in the filter media, impairing its  
ability. In order for your filter to backwash and rinse properly, your pump must be capable 

of providing the backwash flow rates indicated on page 4. 

Check Your Pumping Rate 

Two water system conditions must be checked carefully to avoid unsatisfactory operation or 

equipment damage: 
 

1.  Minimum water pressure required at the filter tank inlet is 20 psi. 
2.  Measuring the pumping rate of your pump: 

With the pressure tank full, draw water into a container of known volume, and measure the 
number of gallons drawn until the pump starts again. This is draw-down. Divide this figure 

by cycle time and multiply the result by 60 to arrive at the pumping rate in gallons per min-
ute (gpm). To aid in your calculation, insert the date in the following formula: 

DRAW-DOWN ______ ÷ CYCLE TIME _______ x 60 = PUMPING RATE ________ (gals) 
(secs.) (Gpm) 

 
EXAMPLE:  

CYCLE TIME is 53 seconds.  DRAW-DOWN is 6 gallons; then, PUMPING 

RATE equals: 

6 gallons ÷ 53 seconds x 60 = 6.8 gpm 

See chart on page 4 for minimum flow rates. 

 
NOTE:   If your pumping rate is inadequate for the model, do not install your filter until 

the problem has been corrected. 
 

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