Hi -

I've had my Zodiac Clearwater LM2-40 unit since March 2002 and I'm seeing the same thing as you are seeing. I used to acid-soak the cell every 6 months or so (sometimes I got lazy and let it go for a year), for the first few years, but lately (since the beginning of 2006), I'm seeing that the calcification of the cell plates is happening every couple of weeks or so (not as bad as your unit). I

'm also seeing that the concentration of acid required to clean the cell plates effectively is getting to be stronger and stronger. For the first couple of years, I noticed that cleaning the cells required a mix of 1:5 ratio of acid-to-water. Now, I use full strength acid and its every couple of weeks or so.

My guess is that using full strength acid is not good for the cells (someone told me that it damages the cell, but have no further information on this), but if I don't use full strength acid, it can't get rid of all the calcification on the plates. I tried using 50% strength acid, and it can soak the entire day and not get clean. I got frustrated and started going full strength - which cleaned the cells in a few minutes.

Anyways, I've noticed that since then, my chlorine production has been very weak and I'm guessing that my cell unit needs replacement. Its been over 4 years now, and I'm told that's about the lifetime of the cell. After carefully examing the cell plates, I've noticed that the corners on some of the plates have been corroded off due to the calcification.

I looked around the Internet and saw that the cell unit replacement is a whopping $550. The full unit new is about $900 now. If I think about the cost of the unit over the last 4 years and what its saved me as far as chlorine and maintenance, I'm still thinking that it was a good investment.

I think what I would do differently if my unit was new would be to be religious about acid soaking it with a weaker strength solution but more frequently than I did (every quarter rather than every 6/12 months). I don't know if that would have changed anything, but I'm guessing that getting rid of calcification before it had a chance to really build up might have helped some.

Overall, I'm still pretty pleased that the cell unit I have lasted as long as it did. Time to bite the bullet and take out 5 bills!!

Ben