Have you ever had the problem where your filter pressure just would not come down, or maybe it would come down for a few hours after backwashing, but then it would go right back up again? This is a problem that is known as “short cycling”
On a DE filter, not all the DE is backwashed out every time you backwash the filter. This results in a buildup of DE and dirt inside the filter that gradually reduces the effective filter area to the point that you may be only cleaning off 10-15 square feet of filter area when you backwash. A thorough cleaning of your DE filter should restore it to its original filter cycle times.
On a Sand filter, over time, the sand becomes clogged with dirt and oils and that will reduce the effective filter area. When this happens, the best solution is to replace the sand with fresh sand.
On a Cartridge filter, if your pool turns green, the algae in the water will put a fine coating of slime on the filter material and your filter pressure will jump and your flow will be reduced to nearly nothing. The ONLY solution in this case is to break down the filter and clean it. Shocking the pool will remove the green, but it will not remove the slime coating on the cartridges.
The grids in a DE filter or a the cartridges in a cartridge filter can become clogged with oils or minerals over time. You can try a filter cleaning chemical, but that seldom works. Usually by this time, the grids or cartridges are old enough that they should be replaced anyway.
DE filters particularly need a refresh time. If you run a DE filter 24 hours per day, the pressure will often run high fairly quickly. This is because when you run a DE filter, the DE becomes tightly packed onto the grids. When the pump turns on again in the morning after several hours of off time during the night, the DE will have loosened up and the filter pressure will be lower.
There may be situations where you need to run a DE filter 24 hours per day, but if so, be prepared to backwash it every day or two, especially if the pool is loaded with algae, dirt or debris.
This is one of those “duh” things, but if your filter pressure stays at 40 psi, even after you turn the pump off . . . you have a bad pressure gauge. We get a few of these calls every year.
You may have a blockage in the system
Your filter pressure gauge is measuring the backpressure in your entire pool system, not just the backpressure in the filter. If your pressure is running unusually high, it could be that something downstream is creating a log of backpressure.
Closed valves – if all your valves are closed on the return side of the system (the valves that return the water to the pool or spa) then you will create a dangerous high pressure situation. Be careful when changing valve settings and ALWAYS watch your pressure gauge when turning on your pump.
Mechanical blockage – sometimes things break and come loose inside the system. These small pieces and parts can become lodged up against other components and create a tight blockage. When this happens, your filter pressure will jump. Don’t ignore issues like this.
Ice – if you are restarting your system after a freeze, be careful. Ice can block a line and create a dangerous high pressure situation.
BE CAREFUL: If you are backwashing during freezing weather, be especially careful. A backwash line that does not drain properly can remain full of water that will turn to ice. This ice can create a complete blockage of the line and potentially blow up the filter in your face. If possible, defer backwashing until after freezing weather passes. if you must backwash, watch the pressure gauge carefully and be prepared to shut the pump off quickly if the pressure rises above 30 psi.
Clogged spa jets – your system pressure will normally jump when in spa mode because you are forcing the water through the small venturi jets in your spa. That is fine. If your flow is also reduced (and perhaps your heater keeps turning on and off), then you may have clogged jets in your spa. This can be a bit tricky to resolve.
If you are not sure what the problem is, and you need a professional solution, call us at Pool Stop and schedule a service call with one of our repair professionals. If you have not had a filter clean in a while, it might be best to simply call and schedule a filter clean.