Certified Pool Operator Practice Test

What is the necessary backwash rate to achieve proper agitation in sand filters?

1. 10 gpm/sf

2. 15 gpm/sf

3. 20 gpm/sf

4. 25 gpm/sf

The correct answer is: 10 gpm/sf

The necessary backwash rate for proper agitation in sand filters is 10 gpm/sf. This means that for every square foot of surface area in the sand filter, the backwash rate should be 10 gallons per minute. Option B (15 gpm/sf) and Option D (25 gpm/sf) both have higher backwash rates, which may cause inefficient use of water and potential damage to the filter material. Option C (20 gpm/sf) is also higher than the necessary rate, though it may still work in some cases depending on the specific filter and its design. Ultimately, option A is the most accurate and appropriate choice for achieving proper agitation in sand filters.