Clean your pool filter when the pressure gauge reads 7-10 PSI above your normal clean pressure — not on a calendar schedule.
Understanding how and when to clean your pool filter, along with proper filter maintenance literally separates those who are frequently frustrated with their pool, and those who say pool maintenance is easy. I’ll assume you read my article discussing which filters are best. This article is for both inground and above ground swimming pools.
I want you to first understand filters are designed to maintain clean clear pool water, They are NOT designed to clear a pool with thick algae or a lot of debris. You can skim the top, and should, you can vacuum thick sediment to waste bypassing the filter, and you should, then you’re stuck filtering what’s floating in the water.
Lets first answer the primary question of when do i need to clean the filter.
How Do I Know When My Filter Needs Cleaning?
The short answer is when the filter gauge goes up 7-10 pounds from normal (indexed when the filter was new or clean). If you don’t know the reading from the last time the filter was cleaned, it’s time to clean the filter and index the gauge! All pool filters have a gauge (many don’t work), and there is a reading when the filter is clean, and a reading when the filter is dirty. You can’t know when to clean the filter if you don’t know what a normal reading is.
Normal Filter Gauge Pressure = Clean Filter – Time to clean = 7-10 lbs. higher than normal pressure.
*Warning* – Nowadays, people have a 2-speed or variable speed pump. If you increase or decrease the pump speed, the filter pressure will change. So index the gauge when the filter is clean, and the pump is running at the same speed – No worries if you’re running a one speed energy hog of a pump.
Signs Your Filter Needs Cleaning
Cloudy water may, or may not be a sign that your filter needs cleaning, you may just need to run your pump longer. If you’re running it plenty, it’s a sign, Back when I used to do weekly pool maintenance I had a customer named Harry from Methuen. He had a great DE filter I kept clean, so when i showed up and the pool was cloudy, I had to have a talk with Harry. He was from the great depression era and was trying to not use to much electricity.
Sign 2: If you’ve lounged pool side long enough, you might have noticed the current /strength of the water coming back to the pool. With a clean filter the water circulation is strong, you can actually notice a drop in circulation strength before the filter gauge ever creeps up.
Understanding Filter Pressure
Doesn’t matter if you have a sand, DE, or Cartridge pool filter, the same thing is happening. Water flows into the tank pushed in by the pump, then the water is forced through the media to strain out the dirt. once the media clogs up with dirt it takes more pressure to get the water through, and the tank pressure rises, you could call it backpressure. Same reason the flow gets weak.
If you clean your filter and the strong flow doesn’t return, and or the pressure stays high, it’s time to replace the sand, the cartridge, or DE grids/fingers.
*caveat – You can completely clog a clean filter in 5 minutes if you’re vacuuming heavy debris and algae.
Seasonal Filter Maintenance
Pool Opening / De-winterizing
If you have an inground pool with mesh safety cover, you likely have a lot of dirt and algae on the floor and walls, do a quick vacuum to waste completely bypassing your filter! Remember you can skim the top and you can vacuum the bottom, but you can only filter what’s hanging in the water, so before you take that pool cover off and just brush the shit out of the pool mixing all that mess into the water, do a quick vac to waste, most inground pools are over filled in the spring anyways from all the snow or rain over the closed season.
If you have an above ground pool, your pool should open as clean and clear as you closed it, I’ve seen a ton of people pump off most of the pool cover and then try to remove the cover with 5-10 gallons of concentrated muck, use a 5 gallon bucket and get it all off or risk dumping that muck into the pool. If your cover fell in over the winter, Leaf rake and wait for everything to settle to the bottom and do a quick vacuum to waste. Pool filters are not designed to handle this much crapola.
If your filter gets banged up during opening, I would freshen it up, also if you open early as I recommend – 1st because I like non-ice bath ice baths, and also so the pool is ready for the season. You’re likely going to have to deal with a lot of pollen and seed the trees dump until summer season, keep your skimmer baskets cleaned out and watch that filter pressure, it’s likely during this season you may need to do an extra cleaning
Summer Season
This is easy living! Once you get past the opening and spring pollen and seed dropping season, summer is usually pretty maintenance free. With a good pool filter properly sized you should get to the season closing without needing to service the filter again
Pool Closing / Winterizing
Clean the filter! That’s it, give it a thorough cleaning, don’t let the dirt bake on over the winter season. Ever notice dishes are easier to clean when the food hasn’t dried up and plastered on?
In conclusion
I hope you have found this article helpful are now better able to access when to clean your filter and how often. If you’re in Massachusetts or Southern NH and need help opening your pool this spring, or have a filter or equipment issue you can’t figure out, click here to book a pool opening or service repair.
FAQ’s
Why does my pool filter get dirty so fast?
You may have an undersized filter, or your media may need to be replaced, meaning the sand or cartridge element in the tank. Or you may be asking it to do what it isn’t designed to. If your pool cover falls in with a lot of debris, or you have a massive algae bloom, you need to leaf rake out debris or vacuum to waste the heavy stuff before you turn on your filter
Can I damage my pool filter by cleaning it too much?
Absolutely, You can damage cartridge filters the easiest, especially if you’re using a pressure washer, I don’t recommend using anymore water pressure than normal garden hose pressure. Also, sand filters actually work better as they age, while pressure does rise, it also means narrowing paths for a better filtering.
Does clarifier damage pool filters?
Yes, every filter type! It’s my opinion if you’re using clarifier something has gone horribly wrong. Often recommended at pool stores by people who never cared for a pool, or had to replace a filter out of their own pocket. With sand filters it can create channeling, this means channels develop through the sand where by the water passes through the filter unfiltered through channels. And DE and Cartridge filters permanently lose interior filter area, this permanent damage is like downsizing your filter.
If your sand filter is taking too long as it doesn’t filter as good as DE or Cartridge filters, add a pound of DE to it.
