So an 85,000 litre outdoor pool recently been re grouted, replaced loose tiles, removed all the black algae etc.
Re filled with fresh water from a bowser / tanker.
During last month added 5kg of Dichlor granules and 2 KG of Trichlor tablets.
Today using the TAYLOR K-2006 test kit got the following readings
Free Chlorine 5ppm
CYA 50ppm (did this three times)
did not do a Calcium hardness test as water is approx 12 degres C.
Pool looks great. My question is how can the CYA test be so high. Based on manufacturers chemical spec Dichlor per 200 grams will treat 15,000 litres with 1ppm of free chlorine and 0.9ppm of CYA. Trichlor per 200 grams 1ppm (free chlorine) and 0.6ppm (CYA) per 15,000 litres.
If the CYA really is 50ppm I am happy, but it just cannot be when the free chlorine is measuring 5ppm which is approx what has been added. Even allowing for rapid chlorine evaporation before the CYA level stopped it, and even allowing for high chlorine activity from organic contamination (not likely in a clean pool and with cold water) the CYA still would not be this much higher than the chlorine level within a month!
Whenever I test pools for CYA the readings are usually far too high (greater than 100) but this is to be expected where tablets and granules have been used for years. Since taking over these pools I have stopped the use of tablets and granules using only sodium hypochlorite (liquid chlorine). Plus all pools over the winter period are being vacuumed to waste then topping up with fresh water to dilute the CYA. Even the salt pools CYA tests come in around the 50ppm mark. I am 99.999% sure I am doing the test correctly. Because where pools have had 50% drains for repairs and then re filled the CYA will be 50ppm or thereabouts. Just to be sure this is what I am doing...
- sample water taken using 1 litre jug dragged accross the deep end in the pool net approx 2 - 3 foot below the surface
- 7ml added to sample bottle
- 7ml CYA reagent added
- Mix thoroughly for a min 30 seconds.
- Then do the FAS/DPD chlorine test, PH demand test, TA test. (Not doing calcium water too cold).
- Record all information (using evernote in mobile phone which syncs to PC good program for this work)
- Now return to the CYA sample, mix for another 30 seconds.
- Slowly add to the test tube watching the black dot. Once it finally dissapears read the value on the side of the test tube and record.
The only thing that occurs to me is water temp? However Taylor say this does not matter.
Your views / experiences are greatly appreciated.
P.S great web site