OK I am new here We had a nitrate problem last year and guess it carried over this year. Brought water to be tested and the guy was stunned by the nitrate number. Suggested draining and refilling instead of dumping a ton of $$$ on chemicals. We are almost drained...my question is should I do anything b4 we refill??? It is a concreate pool DE filter about 48,000 gallons. Should be brush? Scrub walls? Powerwash??? Or just refill it......any help would be greatly appreciated!!!!