Welcome to TFP!!
It is unfortunate that many times advice given causes other problems..
The first thing we always suspect when folks have issues like yours is that there are chemical imbalances. Pool stores like to say things like you posted, that "everything was great". The question is "great" to what standards. We base our pool care system on accurate testing and only adding what the pool needs, when it needs it. To do that you need your own accurate test kit. I would say order a
TF100. The only other real option for a test kit is a Taylor K-2006. Be careful comparing prices because the K-2006 comes in sizes, designated by a letter. The basic K-2006 has .75oz bottles. You need to get the K-2006-C to get the larger bottles that you want. Even then it is a little short on the reagent & powder for the FAS/DPD test.
The pool store test is a "snapshot" in time, while we diagnose problems with what is called an
Overnight FC Loss Test (OCLT). Only two things cause the chlorine levels in a pool to go down, organics in the water (like algae) and the UV rays of the sun. Through the OCLT we can prove/disprove if something unseen is growing in the water.
The other problem is that the pool industry refuses to recognize the connection between CYA/Stabilizer and the ability of chlorine to do it's thing sanitizing the water. others here can give you the scientific details if you want, but lets just say CYA locks the ability of chlorine to sanitize. The key point is that the more CYA you have the more chlorine you need to keep in the pool to keep algae at bay. I took over my pool with a CYA of about 250 (CYA tests above 100 are just a guess, not very specific contrary to what the pool store says). With a CYA of 250 I had to keep my chlorine level at around 20 just to keep algae away. As you can see, if your pool has high CYA levels then the recommendations of the pool store to have your FC at 4 just won't be as "great" as they imply.
We need to see specific test results from your test kit, not the pool store. Not much credence is given to pool store testing around here. While you would think that a "professional" would be the best, unfortunately in most cases it is quite the opposite. Between employees who blindly trust the word of chemical sales representatives and high school kids working in the pool store for the summer you end up with poor results from their testing.
A little more detail about your pool would help including all the equipment. It is best if you
edit your signature and add the following information so we can better frame our answers to you.
- The size of your pool in gallons
- If your pool is an AG (above ground) or IG (in ground)
- If it's IG, tell us if it's vinyl, plaster/pebble, or fiberglass
- The type filter you have (sand, DE, cartridge)
- If you know, tell us the make and model of your pump and filter.
- List any other equipment you have: SWG, second pump, etc.
- Please mention if you fill the pool from a well or are currently on water restrictions
Information in your signature will show up each time you post and it makes advice more accurate as we know what equipment we are dealing with.
