Make Filter Media Last

Like any other pool component, filter media must be maintained to ensure a long and productive life. But what exactly does that mean? Are pool operators doing what is expected to stretch every dollar to capacity?

How often should you backwash your pool’s filter? Hawthorne Gospel Church, Hawthorne, NJ

Take a look at the recommendations below for backwashing and cleaning a cartridge filter properly.

How often should a filter be backwashed?

Backwashing is defined as the process of cleaning a swimming-pool filter by reversing the flow of water through the filter. Only sand filters and diatomaceous earth (DE) filters can be backwashed.

Many use this process as a “cure-all” technique for problems ranging from cloudy water to unbalanced chemicals. Backwashing, too often and when not necessary, is essentially like creating a leak. When the pool has a leak, it loses more than just water.

During backwashing, fresh water must be added to a pool to cover what was removed during the process. As a result, the fresh water dilutes the current water chemistry, which amounts to additional expenses for more chemicals and water, as well as sewer in many areas.

Pools with heaters also incur costs to return the temperature of the water up after adding fresh water; the heater must operate more to maintain the temperature, which increases utility costs, such as gas and/or electric.

The amount of labor also increases when the 3 to 5 minutes a day spent backwashing is considered.

Ultimately, backwashing should not be done according to a predetermined schedule; rather it should be based on pressure differentials.

Why and when should a filter be backwashed?

For sand filters, manufacturers recommend backwashing only when the filter pressure reaches 8 to 10 pounds per square inch (psi) above the previous time the filter was backwashed.

Filters should only be backwashed when needed, not on a regularly scheduled basis. Island Breeze HOA, Manahawkin, NJ

On filters with both influent and effluent gauges, the differential should be 10 to 20 psi between the gauges. As the filter becomes dirty, the dirt clogs the pores in the sand and helps the filter to hold even smaller particles. Therefore, as the filter media become “dirtier,” they are able to filter down to a smaller micron and work more efficiently.

For DE filters, backwashing is recommended when the pressure reaches 10 psi over normal operating pressure. With DE filters in some areas, a separation tank is required to collect the backwashed water, which includes DE. When a DE filter is backwashed, fresh DE needs to be added after the process to recoat the screens.

For any filter, backwashing should be performed for 3 to 5 minutes or until the sight-glass clears.

When a pool or spa has cloudy water, it is often due to one of two causes–water balance or filtration. Upon testing the water chemistry–if the readings are within acceptable ranges per the state bathing code–it is time to inspect the filter and recirculation equipment.

The first check is the flow rate per the flow meter.

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