Pool chemistry messed up

I was on vacation for the last 3 weeks and when i returned the water chemistry was all screwed up.

Free chlorine -over 20.2ppm
Total chlorine-over 20.2ppm
Combined chlorine - 0ppm
Ph-6.6
Hardness-90ppm
Alkalinity- 7ppm
Cyanuric acid-84ppm
Copper-1.2 ppm

I just replaced the pool heater and I'm worried about the low Ph and Alkalinity will eat away the copper heat exchanger,but the installer said not to care because the results are masked by the high cyan uric acid content.
Is he right or should i add some washing soda?


Pool size 25000 gallons
Solar cover on.
Ontario,Canada
PS
I couldn't find the washing soda at the local Walmart.Any other places that carries the washing soda?


Thanks,

Julian

High CYA does NOT reduce the effect of low pH on pool equipment; your installer is wrong.

BUT . . . with chlorine of 20.2 ppm (how did you test?), phenol red testing for pH will not be accurate. However, the Alkalinity = 7 ppm, when CYA = 84 ppm (bogus test result, BTW -- there is no field or dealer method of testing that can distinguish 80 ppm from 90 ppm CYA) suggest your REAL pH may be lower than 6.6.

Buy borax (better for your pool) or soda ash in the detergent section of MANY grocery and big box stores.

Thank you for the quick response.I think i was not clear.He never suggested that there will be no damage because of the low pH and alkalinity but the Ph and alkalinity reading where wrong because of the the high CYA.He suggested to empty the pool about 6" and refill and the take the test again.Is running this low ph water through the heater will do too much damage to the heater or should i run a bypass to avoid running through the heater?
How much borax or washing soda should i add?


Thanks,

Julian

http://www.poolcalculator.com/

Don't dump the prescribed amount in all at once. Add some, wait an hour or so, then test again.

Good Luck!

Here is a calculator that we like better:

http://www.poolforum.com/zxq/BleachCalc262.exe

It is more than just a bleach calculator. If you click on the drop down menu in the upper left-hand corner, there are other calcs.

However, Jason is right that you add a smaller amount than you think you need, test, add more if needed. The exception to this is bleach. When adding bleach, you need to add enough to get to the chlorine level that will be high enough to sanitize your pool.