If you're seeing sand in your pool, and you have a sand filter, the most common culprit is a cracked or damaged lateral inside the filter.
Here's a breakdown of why this happens:
How a Sand Filter Works (Simplified)
- Pool water is pumped into the filter tank.
- The water flows down through the sand bed, which traps dirt and debris.
- Cleaned water is collected by a series of laterals (small, slotted tubes) at the bottom of the tank.
- The laterals direct the filtered water up a standpipe and back into the pool.
Why Laterals Fail
- Age and Wear: Over time, the plastic laterals can become brittle and crack.
- Improper Winterization: If water freezes inside the filter, it can damage the laterals.
- High Pressure: Excessive pressure within the filter can stress the laterals.
- Incorrect Sand Type: Using the wrong type of sand can clog the laterals and put undue pressure on them.
- Physical Damage: During maintenance or sand replacement, laterals can be accidentally broken.
Identifying a Damaged Lateral
The most obvious sign is sand in your pool, especially after backwashing or rinsing the filter. Other symptoms may include:
- Cloudy pool water.
- Reduced water flow from the filter.
- Higher than normal filter pressure.
How to Fix the Problem
- Turn off the pump and disconnect the filter.
- Open the filter tank and remove the sand. (You may need to scoop it out.)
- Inspect the laterals for cracks or damage. Pay close attention to where they connect to the manifold (the central hub).
- Replace any damaged laterals. Lateral sets are available online or at pool supply stores. Make sure you get the correct size and type for your filter.
- Reassemble the filter, being careful not to damage the new laterals.
- Refill the filter with the correct type and amount of filter sand.
- Backwash the filter thoroughly to remove any fine particles.
- Rinse the filter before returning it to normal operation.
By understanding how your sand filter works and the potential causes of lateral damage, you can quickly diagnose and fix the problem of sand returning to your pool. This will help keep your water clean and clear.
