Hot Tub Filter Components page 3

In normal filtration, water comes into the valve through the opening marked "Intake" or "From pump discharge." After passing through the filter media, the water flows on to the heater or back to the hot tub. When the valve is rotated into the "backwash" position, water is sent in the opposite direction, removing dirt (and DE, if the filter uses that medium). The flow is then directed to the opening marked "Back wash," which is connected to a waste or sewer line. Many backwash discharges are not hard-plumbed, and you must connect a hose to direct the wastewater wherever you want it to go. Normally a cheap, blue, collapsible plastic backwash hose is attached to the waste opening with a hose clamp. This 11A- or 2-inch-diameter (40- or 50-millimeter) hose is intentionally made rather flimsy, since the water will not be under much pressure when draining to waste and to allow the hose to be easily rolled up and stored near the filter. This ease of rolling up is an advantage since backwash hoses normally come in lengths of 20 to 200 feet (6 to 60 meters)—you may have to route wastewater into a street storm drain, so very long lengths are common.

By the way, dirty filter water is an excellent fertilizer for lawns as it is usually rich in biological nutrients, algae, decaying matter, and DE (which, as you now know, is a natural material). You may run your backwash hose on the lawn or garden, providing the water chlorine residual level is not above 3 parts per million (ppm). Chlorine levels higher than that may "burn" the grass!

Some rotary backwash valves also include a rinse feature, so that after the water has backwashed through the filter, clean water from the pump can be directed to clean out the pipes before returning to normal filtration. This prevents dirt in the lines from going back to the hot tub after backwashing. Do not rotate any backwash valve while the pump is running, or you might damage the valve and the pump/motor.