I can't answer your question about if the altitude affects the procedure or not.

But, I can tell you that your FC is WAY too low for a pool with a CYA of 100 and is a big invitation to algae. Plus, the fact that the CYA test cannot differentiate past 100 means that it could actually be much higher than that. Take a look at the Best Guess chart in my signature below.

You have two options:

1. Do a partial drain and refill and try and lower the CYA to a more manageable level. Do NOT totally drain a pool however.

OR

2. Run higher than normal chlorine levels to compensate for the high CYA. (Again, see the Best Guess chart.)

Either way works. Just a decision you need to make. If you do nothing and continue to have chlorine between 1-3, you WILL get algae though.

I'm assuming from the way you reported your testing results in ranges that you are using test strips. Is that correct? We don't feel that test strips are too reliable or accurate. You really need a good test kit. The one we recommend is the Taylor K-2006 or 2006C (same kit, larger bottle of some reagents). If you buy it through the Amazon link in my signature, the Pool Forum makes a little money on the sale which helps us keep this form online. Only buy if the seller is Amato Industries, however. Some other sellers are substituting the K-2005 which you do NOT want.

If you decide to go with option #2 above, you MUST have this kit. Other kits cannot test high cl levels like you would need to run. But, even if you go with option #1, it would still be a good idea to buy it. We like everyone to be able to test their own water with good results. It makes pool maintenance so much easier.

Welcome to the forum, BTW. Hope you enjoy it and find it helpful to you!

EDIT -- Looks like Jan posted while I was typing. Advice is pretty much the same. BTW -- I'm going to ask Ben to take a look at your question about if altitude affects the aeration process and get his take on it.