Sand Filters have been known to last for years with little-to-no issues. Proper care will keep your Sand filter working strong and efficient each season. Let’s dive into some basic Sand Filter Care tips to ensure that your pool is getting the best filtration possible!
Backwashing Sand Filter
Do you know when to backwash your sand filter? Or, is just part of your routine pool maintenance? The most obvious clue is walking out to a pool full of cloudy water. If it ain’t clear, it ain’t clean! In other words, if the water is murky, the water circulation may be weak or there is a chemical imbalance.
Let’s look at the first clue – is your pool getting proper circulation? The easiest place to begin is your pool filter’s pressure gauge.
If your filter system has inlet and outlet pressure gauges:
- When the pressure differential reaches 18 – 20 psi, it’s time to backwash your sand filter. As the sand bed builds up with dirt and debris, the pressure differential will increase. This is because it takes more pressure to push water through the large amount of dirt in the sand bed.
If your filter system only has an inlet pressure gauge:
- You will need to backwash when the pressure increases by 8-10 psi from the initial reading (post backwash). An easy tip is to mark the pressure gauge with a grease pencil or tape after a good backwashing. Or write down the running pressure during each cleaning cycle.
Keep in mind that filter cycles can be impacted by different factors: Heavy bather load from a recent pool party or wind-blown dirt from a recent storm. Algae blooms can also affect the filter system’s efficiency. If your sand filter is connected to a newly plastered pool, it will be filtering plaster dust; which quickly clogs the filter. For new pool installations, we recommend extending the backwash duration to 2x or 3x longer than usual to remove the plaster dust.
Water Flow During Backwashing
Take note of the water flow next time you backwash the pool. Most manufacturers advise to backwash up to 3 minutes. Double-check your filter owners manual to verify their recommended backwashing duration. After backwashing is complete, and the pump system is off, set the multiport valve to “Rinse”. Turn the pool pump back on for about 30-60 seconds. This will wash all of the dirty water out of the sand filter and send to waste instead of returning to the pool. Once complete, and the pump is off again, set the valve back to “Filter” for normal filtration cycle.
Take Charge of Your Filter
Proper charging of the sand is essential to get your sand filter system off to a strong start. Here is how to do it:
- Purchase the proper size pool filter sand. Most sand filters use .45 to .55 mm, which is commonly called “pool grade No. 20 silica sand.”
- Make sure to cover any vertically exposed pipes to keep sand out of the circulation system.
Before adding new sand to the filter, it is recommended to fill the tank bottom with a few inches of water.
- This will cushion the sand as it enters the tank.
- Also, cover lateral assembly with pea gravel before adding the pool grade sand. This is to prevent any damage.
- Slowly pour the sand through the top of the filter tank. It’s a good rule of thumb to leave about 12 inches of space between the sand bed and the bottom of the diffuser assembly. The freeboard space will prevent sand loss during backwashing.
- Sand Filter owners manuals provide tips on how to charge the filter. Some recommend holding down the vertical standpipe so it isn’t dislodged when the sand is added. Some assemblies are threaded into the top of the tank, while others are secured by a clamp. All assemblies use O-Rings to create a tight seal. Make sure to use an appropriate O-Ring lubricant to ensure the seal.
What about the filter valve?
Sand Filters are designed with one of two types of filter valves: multiport or side-mounted slide valve. Side-mounted valves only have two functions: filter and backwash modes. The most common type of filter valve is a multiport.
Modes on Multiport Valve:
- Set the valve to “Filter” during normal filter cycles. It should stay on the mode most of the time. The valve directs the water to the top of the sand filter, where it compresses the sand. Debris is removed as the water makes its way to the bottom laterals, through the filter and back to the pool.
- Turn your valve to “Backwash” when you are cleaning the sand filter. The valve will direct water to come out the bottom laterals, reversing the flow of the filter tank. This will cause the sand to lift about 7 inches above the normal position, while releasing trapped debris into the water and exiting through the waste line.
- Water is directed by the valve back to the top of the tank, similar to Filter Mode. The sand media is re-seated back in place while sending water out of the waste line. This reduces the chance of particulate blow-back to the pool (from backwashing).
- This function allows water to flow through the valve and bypass the filter. It is used during certain chemical treatments and pool cleanups, allowing water to avoid contaminating the sand.
- This valve mode also bypasses the filter, but this time it sends the water directly out the waste line. This mode is used when vacuuming algae out of a pool or during a new sand filter start-up. Some pool owners will use this function when lowering pool water after a storm or when in need of lowering the CYA level in their water.
Sand Filter Operation
Here are a few tips to help keep your sand filter running smooth each season:
✔ Keep an eye on the pressure gauge
Pay attention to the pressure gauge when the filter is clean. Backwash your pool when the pressure is 5 psi – 10 psi higher than the original amount.
✔ Backwash until water is clear
Make sure to backwash until the water is clear that is coming out of the backwash hose. Unfortunately, backwashing can use between 50 – 300 gallons of water, so don’t step away while using this valve mode. Also, check with your local codes for proper water disposal.
✔ Only switch the valve mode when pump is OFF
When the pump is running, keep the valve in a set position. In other words, do not move the valve handle while the pool pump is operating and pushing water through it.
✔ Don’t backwash too often
Try to avoid backwashing too often. The filter works best mid-cycle, when there is some particulates in the sand bed. This actually help the filter work more efficiently. Also, backwashing will drop your water level; which you will need to replace.
✔ Vacuum while in Filter Mode
Try to avoid using the pool vacuum while your filter is in backwash mode. The laterals may become clogged, resulting in inefficient operation. Even worse – you may need to replace the sand media to unclog the laterals.
✔ Rinse after adding new sand
After replacing the pool filter sand, start the filter in Rinse Mode for a few minutes. Some small particles may have blown into the pool. If this happened, vacuum the debris to waste to avoid re-entry of the particles.