Sand Filter Purge
Dosing based on one Pentair TR-140 commercial sand filter
Have you ever been told that filter sand "wears down" and needs to be replaced after a certain number of years? That seems to be the industry standard explanation to justify costly filter sand replacements, but we don't buy it anymore. We went into a YMCA with 11-year-old sand in it, and we chemically purged it. After just 4 hours and two backwashes, we could not tell the difference between the chemically-refurbished sand and brand new sand. The customer saved thousands of dollars because they did not need the sand changed, and their filter is working great.
Related: How to Implement the Orenda Program
You will need:
Phase 1: Chemicals
- Turn pump off, isolate the filter and open up the lid.
- Lower the water level in the filter to about 2-3” above the sand.
- Collect a handful of dirty sand for before-and-after samples (optional).
- Remove large physical debris (if applicable) prior to adding chemicals
- Add one quart (32 oz.) of CV-600 enzyme and 8 oz. of PR-10,000 phosphate remover to the filter.
- Stir and mix chemicals deep into the sand bed as thoroughly as possible.
- We recommend an air compressor with a long wand. If that is unavailable, use a garden hose, broomstick or something similar to allow chemicals to soak deep into the sand bed.
- Start a timer for a minimum of three hours (the longer, the better). Leave the filter lid off during the wait.
Phase 2: Backwash and Rinse
- After at least three (3) hours, close the filter lid and backwash.
- After backwashing, turn pumps off again, open the filter and inspect sand.
- Collect a handful to compare sand before-and-after (optional).
- If the sand filter is not to your satisfaction, repeat this step after the second backwash.
- Close filter again, and backwash for a second time. This step is very important, make sure you backwash again!
- The first backwash lifts most of the organics out of the sand, and causes suds and foaming. The second backwash flushes all of that out of the filter to waste.
- After the second backwash, run the rinse cycle thoroughly.
- After rinsing, resume normal operation with your newly cleaned sand filter.
For larger filters, extrapolate dosing at teh same 4:1 ratio of enzyme to phosphate remover (CV-600 : PR-10,000). For example, large commercial filters may take an entire gallon of PR-10,000 and up to 4 gallons of CV-600. The 4:1 ratio is important for this procedure to work properly. If you want Orenda’s help, contact us directly. We’re happy to walk you through it.