DE Filter Dilemmas

Years and years and years ago, when I started in the business, people had a choice of sand or diatomaceous earth (better known as “DE”) filters. The sand filter was low maintenance and low efficiency. The DE filter was high maintenance and high efficiency. People had to make a trade off. Fortunately, with newer technology, we now have DE filters with low maintenance and high efficiency. So, if you have an older DE filter and have a lot of these common problems listed below, bear in mind that when it comes to the end of it’s life, you can comfortably upgrade to another DE filter, therefore, giving up some of the hassles without giving up any efficiency. What a deal!

Clogging, Short Cycles, High Pressure

This is extremely common for DE filters. It happens mostly when the pool is not, shall we say, looking it’s best. It can also happen if the filter internals have not been acid washed. Think about how the filter works. You have elements inside the filter whether they are finger-like, grid-like, or large cartridges. The DE powder that you pour in through the skimmer that gets sucked into the filter, coats these elements. Now the water has to pass through the powder, through the elements, and back to the pool. Once the filter picks up enough debris or algae, it coats the powder. Now the water can’t get through the filter as fast because it has to, somehow, get by or through the debris, the algae, and the powder, and the elements. The more particles the filter picks up, the more restricted it is. Because a DE filter is so extremely efficient, it picks up even the tiniest of particles, particles we can’t even see with the human eye. All of a sudden, you notice that the water is barely circulating. The snowball is rolling because without circulation, your chemicals aren’t distributing, if you have a chlorinator then there’s not enough flow to dispense chlorine, your heater isn’t working without flow, and you can’t vacuum. Why isn’t the water circulating…because it can’t get through the filter, there’s too much “stuff” in its way.

Now you realize that you better backwash or hose out the filter. I hope you put enough DE powder in there because this is what the dirt and algae attaches too and, when you backwash, the powder and the debris all washes out. If you didn’t put enough DE then you left bare spots on those elements and when the dirt and algae entered the filter, instead of attaching to the powder, it ground into your filter elements. Uh oh. That ground in debris doesn’t just hose off nicely the way you would like it to. That filter is mad at you. You have to acid wash it now. The debris grinds right into the fibers.

Remember, that filter filters out particles too small to see. Even if the filter doesn’t look that dirty after hosing it down. If you haven’t acid washed that filter for over a year, it could very well be imbedded with fine microscopic particles which could restrict your flow. It’s worth the fifteen dollars for Filter Cleaner or six bucks for Muriatic Acid (see “acid washing”), along with a little effort, to take care of those elements once each year or after a heavy algae incident. Not to get off track but we can tell you how to avoid those algae incidents by the way (see “clear water recipes”).

Back to your filter. Let’s assume you did everything right. You had acid washed your filter in the past year and you had added enough DE prior to backwashing. Great job! Now, when you backwashed or hosed out the filter, all the DE powder and all the algae and debris hosed out nicely. You set your filter back up, turn it on, put the proper amount of DE into the skimmer (see “DE charts”), and you’re back in business. The filter pressure is normal again and the water is circulating. It’s all systems go. If your pool is still green or fairly dirty, you may have to repeat this process several times until all the particles causing the problem are removed from the pool. Algae is a plant growth. You can kill the algae with Shock Treatment but, unfortunately, it does not dissolve and it needs to be filtered or vacuumed out. Vacuumed…that’s a good point. When you vacuum, where does the debris go? Into the filter…that’s right. What does that do? Yup, it coats the powder that coats the elements that clogs the filter…and we start all over again. Don’t get discouraged though, see “service tips” for some ideas to speed this process along.

Let’s look at the alternative for a moment. What if your filter didn’t pick up all those fine particles…then it wouldn’t clog so fast, the circulation would stay strong, the heater would keep working, the chlorinator would be chlorinating, you wouldn’t have to keep backwashing so often, and you would still have enough suction to vacuum. Perfect as long as you don’t want to swim because your pool still looks lousy and the debris you are vacuuming is going right through your inefficient filter and back into your pool. Other than that, you’re set.

It’s not really as bad as it sounds. Picturing and understanding how your filter works, allows you to understand your objective and to be able to tackle the problem. Most people encounter DE filter aggravation in the spring due to an algae-filled pool that miraculously appeared sometime between when the pool was closed and then opened. Once the initial cleaning is done, the rest of the year is a joy. Shocking heavily upon opening helps to kill any algae. Once settled, algae can be vacuumed out with the filter set to “waste” position or with the drain valve 20% open. The pool can then be refilled, tested, and balanced. To alleviate heavy algae growth in the spring, add a strong algaecide at closing and then again in March upon thawing before the pool is even opened. We recommend Pristine Blue or Algae Shield for vinyl-lined pools and Family Pools Poly 60, which contains no metals, for Gunite pools.

We hope that we have given you a better understanding of your DE filter and now, maybe you’ll appreciate it a little more knowing that any aggravation that it has caused you is because it is such a good filter and giving it up for a less efficient filter wouldn’t necessarily be the right choice. If anything, inquire as to lower maintenance filters such as the Sta-rite Systems III Modular DE filter now available. Please don’t be afraid to take advantage of our years of experience here at Family Pools. Many of our employees have been here for over a couple decades and we would love to share with you what we have learned in that time. If you have a Perflex filter, please see our Perflex tips.

For more information about Backwashing, you can read about it here.

Filter Runs

Just a little elaboration on filter runs where algae is concerned.