pool sand filter refurbish

Refurbishing a sand filter vs. Doing a sand change

To test the strength of Orenda products, we accepted a challenge: refurbish a dirty sand filter in need of a sand change

Paddock built a nice YMCA aquatic center with a vacuum sand filter eleven years ago. Today, it is home to a 300+ athlete swim team, a masters swim team, school programs for learn-to-swim and water aerobics. On any given weekend they can host swim meets of over 700 swimmers.  We consider this a heavily loaded commercial pool.

Fast forward to 2017. That same YMCA is in desperate need of its first sand change. Eventually, there is no getting around it; this sand is not doing the job anymore. The YMCA has been backwashing several times a week, the water has been dull and cloudy, and the sand had channeling issues. The estimated cost of the sand change: $3500. The job involves four guys laboring all day to get the sand out—either by a costly vacuum truck or shovels and buckets—then carry in the 100-pound bags of sand back in to replace it. This particular filter has thousands of pounds of sand that serves about 150,000 gallons.

Rock hill sand filter

Inside the vacuum sand filter at the YMCA

Paddock challenged us to see if our natural chemicals could refurbish the sand, and therefore extend its useful life. In theory, if our CV-600 Enzymes are strong enough, they should be able to soak into the sand bed and break down the non-living organic waste (grease, oils, bather waste of all kinds) that act as a ‘glue’ in the sand bed. This organic waste is what clumps sand together and makes it gross. We travelled to Rock Hill to purge the filter because we accepted the challenge.

Sand filter purge

We met with Dennis Ingram, service manager for Paddock Construction Company. He has been doing these types of sand changes for 12 years, and has done hundreds of them. Dennis remained skeptical of our theory (and for good reason). However, he was hopeful and excited too. If we could refurbish this sand back to its original condition, it would be huge for Dennis and pool service professionals like him.

We used only two products for this experiment: PR-10,000 Phosphate Remover Concentrate, and CV-600 Enzymes. We added half a gallon of PR-10,000, which reacted with phosphates in the water upon contact.

rock hill sand filter purge

CV-600 Enzymes being poured into the filter

We then added one gallon of CV-600 enzymes, and our CEO, Harold Evans, climbed down into the filter with a rake. He raked the sand to try and mix in our products as deep into the sand bed as possible.  After raking for 10 minutes or so, Harold climbed out and we let the natural chemical soak for an hour. We watched the non-living organics rise from the sand bed up to the surface and bubble. The greasy oil-slicks were being consumed by bubbles, which showed us the enzymes were hard at work. CV-600 breaks down carbon waste into CO2 and H2O. The bubbles indicated the off-gassing of CO2. It was cool to see in such a high concentration.

sand filter enzyme purge

Nonliving organics were rising out of the sand filter bed to the surface. They look like oil-slicks.

Fill the tank, watch the bubbles, avoid the smell

When we let the filter tank fill up with water, it looked like a dirty, soapy hot tub. We saw bubbles everywhere, and the entire pump room smelled like a sewage plant. It was disgusting, to say the least. That being said, we all had smiles on our faces, because it meant what we were doing was working.  We filled the tank and let it sit for another hour and continue to soak and bubble. Dennis then backwashed twice, back-to-back.

We noticed a few things after these backwashes.

  1. The walls of the filter were covered in active bubbles, which meant the enzymes were eating the organics that had been caked on the walls of the filter itself.

    sand filter walls

    Enzymes were working hard on the organic films that had built up over time on the filter walls

  2. Unlike before, the sand was moving effortlessly. As if it were light and fluffy, not clumpy and thick. It was a remarkable difference. (See the video above).
  3. The sand had gone from grayish to brown, like new sand. The color change was drastic.
  4. We saw specs of garbage along the top of the filter sand bed. We had to remove them by hand because enzymes do not digest paper and trash.
  5. Dennis noticed that the filter valves were turning easier after being soaked in the enzyme bath for an hour. This was an unexpected benefit of our filter purge.
  6. The smell had largely gone away when we backwashed.
  7. The sand was no longer grimy, clumpy or sticky. It felt like beach sand.

All in all, the purge took about 3 or 4 hours including set up and clean up. We actually had enough enzymes remaining to do a full purge of the 150,000 gallon pool. So we poured the right amount into the refurbished sand filter and left the facility. The experiment was a total success.

You should refurbish your sand filter. Here’s why.

According to a few studies like this one and this one, sand filtration removes microbial contamination and particles from water. This is great for the water itself, but it means that those diseases and other contaminants remain in the sand bed. When bacteria gets lodged in the sand bed, it is hard—if not impossible—for chlorine to kill it. If chlorine could oxidize what was in the sand filter effectively, what we did in Rock Hill would not have been necessary. Who knows? Maybe sand changes wouldn’t be necessary either.

It stands to reason that the vast majority of diseases and other contaminants in a pool system are in the filter itself. We believe that purging the filter with our enzymes is beneficial for the health of the water, because it allows the sand to

  1. allow for better water flow through it
  2. capture more contaminants in the future
  3. release organic waste that protects bacteria from chlorine, which in turn gives chlorine the chance to kill that bacteria.

Results of our experiment

The YMCA saved thousands of dollars, and got a few more years of life out of their sand. It also saved Dennis and Paddock a full day of labor with four guys, and a tremendous amount of heavy lifting. While refurbishing sand will not permanently prevent you from needing to change your sand—friction will eventually wear down the sand itself—it can give you more time. Contact your service provider to learn more about how Orenda can refurbish your sand filter. If needed, have them read this and watch the video above.

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Trackbacks & Pingbacks

  1. […] Like any component to a pool system, sand will eventually need to be replaced. Look up your filter manufacturer’s info to see what they recommend. But don’t be too hasty to decide your sand needs replacing. Perhaps breaking down the organic waste that clumps filter sand together could extend its useful life. […]

  2. […] it may be a symptom of filter channeling. These problems are often caused by heavy organic loads building up in the filter sand and clumping it together. If not just organic loads, calcium can harden in the sand too, as well as […]

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