How to Deal With Pool Filter Pressure Problems

We all know that there is a big difference between a swimming pool and a pond. A pond may be full of wildlife, including algae and other impurities in the water. The water in a swimming pool, on the other hand, should be clean and clear. One of the ways that this is achieved is by carefully balancing the chemicals in the water, especially chlorine. But another vital part of keeping the pool clean is the pool filter. Your filter removes tiny debris from the pool water, keeping it consistently clear. But none of this can happen without water pressure. Pressure produced by the pump keeps water flowing through the filter. To keep an eye on the pressure, every pool filter has a pressure gauge. Knowing how your pressure gauge works and how to deal with pool filter pressure problems is essential to maintaining a healthy pool.

How to Deal With Pool Filter Pressure Problems [infographics]

Understanding the Filter Pressure Gauge

Your filter should be a pretty simple device. Water flows into it, it catches tiny debris, and the cleaned water flows out. There are no moving parts, no electricity, and nothing really that can break. The only regular maintenance is to clean out the filter periodically when it has captured so much debris that water isn’t flowing properly. If you have a cartridge filter, you can take out the cartridge and clean it. If you have a DE filter, you can remove the filter, wash it off, and then replace the DE. A sand filter is perhaps the simplest, only requiring occasional backwashing.

However, the one piece of your filter that really tells you what’s going on–and when you need to clean the filter–is the pressure gauge. A pressure gauge is typically a round gauge that looks like the manual speedometer on many cars. Most gauges range from 0-60 PSI. A small needle will point to a number in that range, and that is your filter pressure in PSI (pounds per square inch).

So what is the ideal pressure? Unfortunately, there is no precise answer to that question. Every filter has its own ideal pressure. Typically that will be between 10-20 PSI, but not always. To find the ideal functioning pressure of your filter, you will have to test it. Clean and backwash your filter, then run it a bit, so it is primed. When the pressure holds steady, write down the PSI. That is your ideal PSI. You may want to take a permanent marker and write that down on the filter itself. You’ll need to know that number to tell when the filter needs to be cleaned and to diagnose any potential problems.

Filter Pressure Is Too High

As the filter gets dirty, the pressure may rise. Other issues can also cause a spike in pressure. As long as the PSI is no more than 10 PSI above the ideal, you don’t have to do much. But when the PSI reaches 10 or more PSI over your ideal, it’s time to clean the filter. Pull out the cartridge to clean it, or backwash a DE or sand filter. If the pressure goes back to the ideal, you’re done.

If the pressure gauge continues to read high after you’ve cleaned the filter, something isn’t working right. Something is preventing water from flowing back into the pool after it passes through the pump. Check for any of these problems:

  • The returns or return valves are closed, partially closed, or blocked
  • Something is wrong with your filter medium (cartridge, grid, or sand) that requires more than just a cleaning
  • Broken parts inside your filter (besides the filter medium)
  • Lime deposits in the pool heater that restrict water flow

If there is a problem causing high pressure, turn off your pump immediately. If the pressure spikes too high, it can cause a filter to rupture, causing severe injuries or even death. Any time you turn on the filter, keep a hand on the switch and an eye on the pressure gauge. If the pressure is in the normal range, you can let go of the switch. If the pressure spikes, immediately shut off the pump.

Filter Pressure Is Too Low

Low pressure in your filter is much less dangerous than high pressure, but it means your filter isn’t doing its job. Low pressure will (almost) always be caused by a problem at or before the pump. That’s because after the pump the water is under pressure so any problems would produce high pressure, not low. Low pressure is caused by an obstruction or other problem that is keeping water from reaching the pump.

Unlike high pressure, there is no normal range for low pressure. If your PSI drops more than 5 PSI from the ideal, it’s time to look for a problem. Here are a few common problems to look for:

  • The skimmer or pump basket is clogged
  • The pump impeller is clogged
  • The filter valve is directing water around the filter
  • Skimmer or main drain valves are closed or partially closed
  • Skimmer or main drain pipes are clogged or collapsed
  • Air is pulling into the system at the pump intake, pump lid, or valves

If you can find an obvious clog at the skimmer, or if you notice that the main drain is blocked, fixing the problem is as easy as clearing the clog. Or, i the problem is a closed valve, opening the valves should return the pressure to normal. However, if there is a clog inside the pipes or the pipes are collapsed, you may need to call a swimming pool professional. Another source of low pressure could be a leak on the intake side of the pump, which would also require professional diagnosis and repair.

Pool Filter Gauge Is Broken

We’ve covered high pressure and low pressure, but sometimes you might get a steady reading but still have a problem. You should be checking your filter pressure weekly and keeping track to see if it is changing. If your filter pressure doesn’t change at all over several weeks, your gauge may not be working. Pressure gauges can fail for several reasons.

If the gauge remains at zero when the pump is on, the problem could be simple to fix. The air bleeder assembly under the gauge, which measures the pressure, could simply be clogged. Unscrew the gauge, clean it out, and replace it. If the gauge goes back to reading something in the normal range, you’ve found the problem. If the gauge still doesn’t move, it could be broken.

Similarly, if the gauge doesn’t go back to zero when the pump is off, you may need a new gauge. Many pressure gauges are cheaply built, and either the needle or the face can warp and become stuck. Luckily, gauges are also cheap to replace. You can usually get a decent pressure gauge for less than $20. When replacing the gauge, make sure to use Teflon tape on the threading for a tight seal before screwing it into place.

The Air Release Valve

Sometimes, air can build up in your filter. One common cause is that the water level is too low and air is coming in through your skimmers. It is a good idea to turn on the air release valve, also called a bleeder, every time you turn on the pump. That’s because air can build up in the top of the filter when it’s not on, which makes the filter less effective. Simply open the release valve and wait a few moments until it starts to spit out water. Close the valve, and your filter will be free of any trapped air.

Diagnosing Filter Pressure Problems

If you have a problem with your pressure and you can’t find a cause, The Pool Butler can help. Our technicians are great at finding the source of pool problems. And once we’ve located the issue, we can get it fixed quickly and correctly. So don’t wait around with pool problems. Contact us today to diagnose and solve your pool problems.

The Pool Butler