Knowing when to clean your sand or diatomaceous earth (DE) filter is vital in keeping your pool water and equipment healthy. Identifying when to backwash your filter might seem compicated but with our help, you'll find that it's pretty simple. There are, however different methods to go about it.
Three common ways to determine when to backwash your pool filter are:
- PSI
- Water Flow
- Water Clarity
What is Backwashing?
Backwashing is the act of reversing the flow of water through your filter media, thereby dislodging trapped debris and flushibg it out through your multiport valve waste line.
PSI
An increase of a quarter or a third of your filter's "clean" operating pressure is a sign of a dirty filter. Pounds per square inch (PSI) is a standard unit of measuring pressure and the most common factor used in determining when to backwash a pool filter. A filter's pressure gauge is the tool used to measure a filter's psi. The face of the gauge is clearly marked off in increments of ones or tens and normally has a maximum value of 50-60 psi.
The "clean" psi rating for individual pools will differ due to variables such as filter size, pump strength and feed of head. The "normal" pressure is the baseline psi reading after a heavy filter cleaning cycle or after the installation of a new filter media. For example, if your normal baseline psi reading is 12 psi then when your gauge reads 15-16 psi (20-25 percent psi above your filter's normal operating pressure) it's time to backwash your pool filter.
There are two types of pressure gauges generally used on filters which include dry case and liquid (oil) filled. The dry case gauges are by far the more common and often the type that's packaged with a brand new filter. The liquid gauges prove to be more durable than dry case gauges. The liquid (glycerine or silicone) dampens the vibrations which are the archenemy of the fragile innards of the pressure gauge.
Flow
A flowmeter is a quick and simple tool for checking filter health by measuring the gallons per minute (GPM) rate through your plumbing line. A GPM drop of one third of the normal flow rate is a sign that your sand or DE filter requires a backwash. For example, if your normal flow is measured at a rate of 30 gpm, a reading of 20 gpm means your filter is screaming, "CLEAN ME!".
There are two common flowmeter styles used on residential pools. The one is the float and tube and the other is a digital format that uses a paddle-wheel mechanism to measure the flow. The flow and tube has minimal moving parts. Fewer moving parts mean fewer things can go wrong. Digital flowmeters are super accurate, but for the simple practice of determining when to backwash a pool filter, they may be overkill.
Pool Water Clarity
Check your pool water for a "cloudy" appearance. You can test total dissolved solids (TDS) to measure how dirty your water is down to the parts per million (PPM). A freshwater pool shouldn't exceed 2000 ppm, because anything higher risks sanitation chemicals losing their effectiveness.
It's important to note that using Waters Choice Pure Enzymes for Pools drastically minimizes the TDS level in your pool.
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