The fundamentals of working with sand filters

Under pressure

Low filter pressures can be caused when lines are blocked before the filter, while high filter pressures can be caused by blocked lines. In most cases, however, it is usually a sign the sand is beginning to calcify. When this occurs, water is channelling between the filter tank body and the sand bed instead of the unit. High pressures usually lead back to the need to change the sand.

Sand in the pool?

Sand returning to the pool usually means one of the filter laterals at the bottom of the filter is cracked or broken and is allowing sand to escape from the filter. This is likely the cause when pockets of sand are found forming on the pool floor, below the returns.

Do not cut corners

When it comes to the internal workings of sand filters, other articles on this subject will likely instruct service professionals to be extremely careful when removing the sand for fear of breaking the filter laterals. However, the best way to go about it is to always replace the laterals when changing the sand.

It is a large job to replace the sand and it would be disastrous to find out after the project is completed that there was a small crack in the lateral, or the filter has started to return sand to the pool. A new filter lateral assembly is a small cost for the customer to ensure they will not have a problem in the near future.

Another common issue with sand filters is when the dial head leaks water out through the backwash line (when the dial is set in the filter position). This is normally fixed by simply replacing the spider gasket in the filter dial head.

Additional advice

The following are a few other tips for service professionals to help maintain sand filters. First, always remove any old Teflon tape on plugs or filter gauges when they are being replaced. Silicone should be used whenever possible as it is less likely to cross thread the plugs or gauges. With clean threads never use Teflon tape. Most importantly, make sure the water is draining from the filter when winterizing the equipment. In the spring, the last thing the homeowner will want to see is a cracked filter they will have to replace.

Brian Lilleberg is a senior employee at Betz Pools with 26 years of experience. He has an extensive knowledge base working with the service and construction departments as well as managing the renovation department. He is currently working as a senior service technician with a focus on water chemistry issues, and serves as a personal representative to select platinum accounts. Lilleberg can be reached via e-mail at blillleberg@betzpools.com.