Backwash - Pentair filter Owner's/Operator's Manual

The pressure in the filter will increase and the flow of water through the filter will diminish
as dirt accumulates in the filter. Eventually, the filter will become obstructed enough with dirt that
it will become necessary to backwash the filter.
Please note that a filter removes suspended matter but it does not sanitize the pool. The
pool water must be sanitized and the water must be chemically balanced for optimum water
clarity. Your filtration system should be designed to meet your local health codes. Pool
chemistry is a specialized area and you should consult your local pool service specialist for
specific details.

1.2 Backwash

The basic principal of filter backwash is to reverse the flow of water through the filter.
This will remove the dirt and debris trapped in the filter bed. For this principal to work properly a
flow of 15-20 GPM per square foot of filter area should pass through the filter in the reverse
direction. This will help to fluidize the sand bed, loosening any solids trapped or compacted in the
bed, and then lifting the solids and transporting them out of the filter to waste. Usually a two to
five minute backwash duration is all that is necessary to clean the filter. Please note, it is
absolutely necessary to have a large enough waste line to accommodate the backwash
flow rate of the filter. A 6" waste line is recommended for all THS series filter vessels.
Tank Cross Section During Backwash Mode
Tank Owner's Manual
9/26/05
Pg. 4 of 23
Rev. D