Backwash run times can be anywhere from 5–20 minutes with rates ranging from 8 to 25 gallons per minute per square foot of filter bed area, depending on the quality of the pre-filtered water. Filtration and backwash rates are calculated by dividing the flow rate through the filter by the surface area of the filter bed.
The pump used for backwashing filters shall have sufficient capacity to provide a rate of at least 15 gallons per minute per square foot (10 L/s/m2) of filter area.
If the manufacturer of the mineral you are using recommends backwash rate of 10 to 12 gpm per square foot, use the low range on cold water and the high range on warmer water.
Backwash Water, (gal) = (Backwash Flow, gpm)(Backwash Time, min) Backwash Flow, (gpm) = (Filter Area sq. ft.)( Backwash Rate, gpm/sq ft.)
At ambient temperature, the recommended filter backwash rate is 6-8 gpm/ft² for anthracite and 13-15 gpm/ft² for sand. Anthracite filters associated with hot process softeners require a backwash rate of 12-15 gpm/ft² because the water is less dense at elevated operating temperatures.
Backwashing is the reversal of flow through the filters at a higher rate to remove clogged particles from the filters. Backwash run times can be anywhere from 5–20 minutes with rates ranging from 8 to 25 gallons per minute per square foot of filter bed area, depending on the quality of the pre-filtered water.
If backwash rates are too high, significantly more media could be lost— compromising filter performance. In any case, it is important to measure, track, and replace any missing media during your annual filter inspection and maintenance check.
Filter & Backwash Velocities:
For DAISY a filtration velocity in a domestic pool of between 20-30m/h and for commercial 15- 25m/h. A backwash velocity of min 45m/h is required for both domestic & commercial. This may vary depending on the temperature and salinity of the water.
Softeners typically have a fairly low flow backwash rate. Usually 2.2-3.2 gallons per minute. You can check this by taking a 1 gallon jug and time how long it takes to fill.
Another industry standard is to backwash when your filter's pressure gauge reads 8-10 PSI (pounds per square inch) over the starting level or “clean” pressure. For example, if your filter is running normally at 15 PSI but increases to 25 PST, you should perform a backwash.
Backwashing too often can reduce the filter's effectiveness. The sediment layer helps improve filtration by trapping finer particles. If you backwash before it's needed, you lose this beneficial layer, which can result in cloudy water.
Backwashing can take only a few minutes to complete, but for a typical pool, it consumes approximately 200 to 300 gallons of pool water! So, while your filter is losing unwanted dirt and debris—your pool is losing a ton of water.
SCHEDULE A HIGHER-SPEED PUMPING TIME
This is an appropriate speed for backwashing and will clear out any air bubbles that can form in the pump and plumbing during the lower RPM period. For an average pool, set the speed to around 2,100 and 2,600 RPM.
You may have a blockage, or have the flow rate set too high. The recommended discharge rate is 12 gallons per minute.
Backashing relies exclusively on return water whose velocity has to be adjusted to the material's granulometry and to the water's viscosity and, therefore, its temperature. In general, velocity is between 15 and 50 m/h or even more at high temperature.
The backwash rate is measured in gallons per minute per square foot (gpm/sf) and varies from pool to pool. The Model Aquatic Health Code (MAHC) recommends a backwash rate of at least 15 gpm/sf, which is standard for most pools.
Most all-residential applications have around an average 5 GPM flow rate.
For rapid-rate pressure filters, the backwash rate should be at least 15 gallons per minute per square foot of filter area.
Turn on the pump and allow the sand filter to backwash for 2-3 minutes or until the water in the sight glass (typically located on the top of the filter) is visibly clear. How long you backwash the sand filter for is not critical though you should visibly see clear water within 2-3 minutes.
Backwash (physical phenomenon), also known as "swash", the backwards flow of air or water. A mixture of beverage and saliva that has flowed back into a drinking vessel.
Filtration rate
For public swimming pools, with high bathing loads, medium-rate filtration is recommended. Medium-rate filters generally operate up to 25m3/m2/h (usually expressed as 25m/h). High-rate filters operate between 25m and 50m3/m2/h.
Updated for 2018. For decades, pool professionals have learned to backwash or clean the filter when the pressure reading increases 10 psi above starting or clean pressure. The growing use of variable-speed pump technology requires a change in this long-understood “rule.”
Backwash is the term used for fluid which makes its way from a person's mouth back into a drinking container. Why is backwash considered bad? If you're sick, you could be putting sickness causing bacteria back into the container and if someone else drinks from it, they could get sick too.
If the pressure gauge continues to read high after you've cleaned the filter, something isn't working right. Something is preventing water from flowing back into the pool after it passes through the pump. Check for any of these problems: The returns or return valves are closed, partially closed, or blocked.