How Much Do You Know About Pool Sand Filter Operation and Maintenance?
Today, we will explain the operation and daily maintenance requirements for quartz sand filters. As is well known, sand filters are the mainstream filtration equipment for swimming pool water treatment and are indispensable to the process. Their primary function is the physical treatment of pool water: contaminants, floating debris, and colloidal flocculants are removed as the water passes through the filter media bed. The filtered water then recirculates into the heating and disinfection stages, enabling water reuse while ensuring environmental friendliness, resource conservation, and safety. Sand filters come in various types, including top-mount, side-mount, and horizontal models.
Precautions for Sand Filter Operation
1. The operating pressure limit is 2.5 kg/cm² (for standard sand filters) or 4.0 kg/cm² (for certain fiberglass sand filters). If the operating pressure consistently exceeds these limits, the filter body, lid, valves, or other fittings may rupture, leading to serious accidents. If the circulation system is subject to high pressure, an automatic valve or pressure regulator must be installed to automatically relieve pressure based on the minimum working pressure rating of the system's components.
2. Sand filters operate under high pressure. If air enters the system (e.g., through piping, pumps, filters, or valves) during operation, it creates pressure; compressed air can cause severe consequences, including personal injury and property damage.
3. The temperature of the water flowing through the filter must not exceed 43°C (for plastic sand filters/liners) or 50°C (for fiberglass sand filters).
4. Always stop the water pump before changing the position of the control valve.
5. Regularly clean the pump strainer and impeller to prevent malfunctions in the pump and filtration system.
6. Sand filters should operate continuously at a medium filtration rate; during periods of low swimmer load or at night, it is advisable to operate at 50% or 35% of the filtration rate. If the filtration rate needs to be increased, the adjustment should be made gradually. Guidelines for Routine Maintenance of Sand Filters
Operations during the running and maintenance of the sand filter must adhere to the following requirements:
1. Clean the pressure gauge connection port and sight glass once a month, and check the operation of the air release valve.
2. Check the accuracy of the pressure gauge and flow meter readings and calibrate them every three months.
3. Open the manhole once a year to inspect the filter media, check for corrosion at the contact surfaces, assess the quality of the sand bed, and replenish the filter media to the design level.
4. As normal filtration proceeds, the filter cake thickens, causing filtration resistance to rise. This is visually indicated by an increase in the pressure gauge reading; when the pressure rises by 30% above normal (e.g., from a normal 1.0 kg/cm² to 1.3 kg/cm²), the filter requires cleaning. Shift the handle on the filter head controller to the "Backwash" position; water enters through the main inlet, flows through the bottom distribution pipes, and rises upward through the sand bed to flush out accumulated debris. Afterward, shift the controller to the "Rinse" position to discharge any remaining debris from the piping. After approximately 30 to 60 seconds, return the handle to the "Filter" position. (Note: Always turn off the water pump power before changing valve or controller positions.)
5. Backwashing the sand filter is recommended under the following circumstances:
① The pressure gauge reading exceeds the initial reading recorded after the last backwash by 50 kPa or more; immediate backwashing is required.
② Continuous operation has reached 5 days.
③ The swimming pool is scheduled to be closed for more than 5 days.
6. Observe the following precautions when performing backwashing:
① Backwashing should generally be performed after the end of a session or at the close of the day's operations; it must not be done while the pool is open to the public.
② If the system has multiple filters, backwash them one at a time; do not backwash two or more filters simultaneously.
③ Control the backwash flow rate and duration; the process should last 5–6 minutes or continue until the discharged water is free of suspended solids. If the system pressure fails to drop effectively after backwashing, it indicates that the quartz sand has caked. Open the sand filter tank, mechanically agitate the filter media layer, and soak it for four hours in a saturated solution of mildly alkaline sodium carbonate (soda ash). Then, drain the tank and perform a backwash; if the results remain unsatisfactory, the filter media must be replaced. During the replacement process, take care to protect the filter pipes to prevent damage that could lead to sand leakage. After replacing the quartz sand, follow the same startup procedures used for a newly installed sand filter. If the equipment is to remain idle for an extended period, leave the sand filter tank empty.
The bodies of large sand filters are molded from high-quality, eco-friendly fiberglass and reinforced polyester materials, ensuring robustness, durability, and resistance to wear and cracking. The spherical design features uniform wall thickness, allowing it to withstand water pressure evenly. With proper use, the filter tank can last for decades. These units are widely used in large swimming pools, competition pools, water parks, and similar facilities.
Intelligent Pool Water Treatment Unit
This intelligent pool water treatment unit integrates advanced electronic systems and equipment. The sand filter is equipped with an electronic automatic valve that can be controlled via pressure and time settings, replacing traditional manual filtration controls. Assembled as a complete unit designed for equipment room installation, it reduces costs associated with on-site installation, material waste, and facility management. It features water circulation, filtration, and disinfection systems, along with intelligent controls, saving you time, effort, and worry.
