Using Pressure Reducing Valve for filter bypass

[edwards1800]

I have a small community water system (approx 8,000 gpd). The water source is from VFD well pumps which maintain 70-80 psi throughout the community. The demand varies greatly, from 5 gpm to (unknown – the max capability of the well pumps is 350 gpm, although domestic peak demand is probably near 100 gpm).

We are adding a treatment system (for taste-not safety) which will have pressure drop proportional to flow. The filter documentation lists the following pressure drops:
7 psid @ 30 gpm
15 psid @ 45 gpm
25 psid @ 60 gpm.

In cases where demand is 60 gpm, I guess the community water pressure would decrease to about 50 psi. If the demand increased above 60 gpm, the pressure would drop further. I don’t think this will happen often, but it should be designed for.

I’d like to limit the amount of pressure drop when demand is greater than 60 gpm by installing a bypass line around the filter and including a pressure reducing valve (PRV) set at 50 psi. I figure that when demand is greater than 50 psi, the PRV will open and allow unfiltered water to be blended with the filter water and meet the demands of the community while keeping the pressure at 50 psi.

Is this the right application for a PRV? Should I use a direct-acting PRV or pilot-actuated PRV?

 

[bimr]

It reads “up to 60%”.

The article states that the amount of energy savings resulting from switching to variable speed pumping is a function of the system curves shape. All system head curves are parabolas, but they differ in their steepness, which is a function of the ration of static head to friction drop of the process served. The system curve is flat if most of the pumping emery is needed to overcome elevation or back pressure (static head), while it is steep is most of the pumping energy is used to overcome friction. Therefore, mostly friction systems, the savings will be greater.