Changing Sand

[Cindy32tn]

I have a vinyl inground pool that holds 28,000 gallons. This is our 4th year and Im having a awful time keeping it from having a green tint in the deep end. My ph and chlorine levels are normal and I backwash regular. I use shock and algecide and it helps for a few days. If my sand needs changing could this be the reason? I have not changed my sand since putting the pool in. Help!!

[aylad]

Contrary to popular belief, you don't ever need to change your sand unless you've gooped it up with some sort of odd chemical, or Baq conversion, or some such as that. My other 3 co-mods, as well as a lot of the other long-time members on this forum, have sand filters with sand MUCH older than yours. In fact, my co-mods each have over 10 years on their current sand! (I would, too, if I hadn't decided to experiment with zeo, but even then my sand was 5-6 years old and I was fine with its performance). If you're having recurrent algae problems, it's because you're not keeping an adequate level of chlorine in the pool. If you post a set of test results for us on your pool water, using drop-based tests, (no strips!!), we'll be happy to help you get that cleared up.

Also, we need to know what the ingredient is that's in your "shock" (dichlor, cal-hypo, etc). You don't really need algaecide--an adequate level of chlorine is the most effective and cheapest algaecide you can use. What's the ingredient in the one you've been using?

Welcome to the forum!!

[Watermom]

Also, please fill out our pool chart with your pool's info. It makes it easier for us to help.

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[Cindy32tn]

ok..i was way off pool is 5yrs old. its 16x32, 20,000 gallons. my ph is is always between 7.2 - 7.6 my chlorine level is always 1.0 - 1.5. i use aqua chem shock..sodium dichloro-triazinetriorie. there is no visible algae. my local pool supply store says i need to change my sand every 3 to 4 yrs..confused?

[Watermom]

Your pool store is wrong, you do not need to change your sand. I recently bought a new filter. The one I had previously had the same sand in it for 12 seasons and it was fine for many more years. I sold that filter and the guy who is using it is still using that sand.

We need to know your CYA reading. A chlorine level of 1.0-1.5 is too low for a pool that is using dichlor. Dichlor has CYA in it and it builds up over time. Chlorine levels are based on CYA levels. The more CYA you have, the more chlorine you need to keep algae away. I have a feeling this is your problem. Take a look at the Best Guess Chlorine Chart in Janet's signature above for more info about that.

[Cindy32tn]

This is foreign to me. What is CYA reading? I am having to backwash and shock ever other day and the green comes back. Ive never had this much trouble with the pool.

[aylad]

CYA is the same thing as stabilizer--it sort of acts like a sunscreen for your chlorine. How high you need to take your chlorine levels depends on your CYA level. Once you know, and achieve your shock level, you have to maintain that level until the algae is dead, and until you can go from sundown to sunup without losing any chlorine.

Janet