longtime BBB owners in AZ?

[twd000]

This is my first year owning a pool in Arizona. I have talked to a few people around town and most have said they drain and refill their pool every 4-6 years. Some longer intervals, some shorter. Most have cited "chemicals way out of whack" or "too much dissolved solids" but didn't elaborate.

I just filled my pool (25,000 gallons from the city was $350 or so) since it was drained while the property was bank-owned.

Of course we have very low rainfall so natural dilution is very slow, and evaporation is very fast. We also don't typically close our pools for the winter.

I'm wondering if I follow the BBB method, if I will still eventually get to a point where it makes sense to start with fresh tap water, or if I could maintain the levels indefinitely here in Arizona?

 

[linen]

My understanding (but I am not from AZ) is that CH level is the one that can cause even BBBers in arid climates to do drain/refills. Often the fill water is already high in CH, then add on top of that very high evaporation rates and at some point CH becomes too high to manage. Some on here have harnessed their roof runoff as a source of dilution to help with this problem.

I will be interested to here more responses to your question from folks in arid climates such as yours.

 

[JohnN]

CH is very high in AZ, which tends to build up over time. There are some AZ residents on here who can elaborate more.

 

[jblizzle]

While I have owned a pool for over 10 years (2 different houses) I have not been pool smart for nearly that long. You can quickly get out of whack with CYA using the wrong chlorine which would require new water, but the CH can be managed even at high levels by maintaining lower TA and pH levels.

 

[twd000]

OK, I'll keep an eye on CH and see how long I can let it ride!

 

[thehowheels]

CH can be managed even at high levels by maintaining lower TA and pH levels.

jblizzle, I was wondering if you could elaborate a little more on this? Any guidelines you can refer me to?

 

[jblizzle]

The problem that develops with high CH can be calcium scaling. This can start when the CSI get to be pretty positive ... like > +0.6
TA, CYA, salt, pH, and temperature all also affect the CSI. By keeping the TA and pH lower (really the only parameters you can reasonably use for control), you can maintain an acceptable neutral CSI even when the CH gets to be pretty high ... like up to 1000ppm.

Play with the numbers in poolcalculator and you can see how they affect the CSI at the bottom.

When I refilled my pebble pool, the CH was around 120ppm, but knowing that it would rise quickly due to evaporation (3 months later I am now at 200ppm), I thought it would be silly to add CH. So, I just kept my pH a little on the high side so the CSI did not get too negative and damage the pool.

 

[thehowheels]

Thanks, I've been reading up on CSI and I've learned something new. Follow-up question -- As CH continues to climb, and pH / TA need to be taken lower, does this pose any risk to bathers? At what point should you just "give in" and drain?

 

[jblizzle]

There is really no danger to swimmers as long as the pH stays in the 7s (and the TA can not really get too low without affecting the pH).

Hard to say when you need to give up, I have never been that high while paying attention. pH is usually happier being in the 7.6-7.8 range, so once the CH gets around 1000, you have a pretty + CSI. :
One example pH = 7.8, TA = 60, CYA = 50, Salt = 500, borate = 0, temp 85
CH = 300 gives CSI = 0.05
CH = 1000 gives CSI = 0.47 ... so scaling could be starting, but if you kept the pH at 7.3, then the CSI is back to 0. The problem is the pH may not want to stay the low for very long.

 

[Melt In The Sun]

I've had my pool for 4 years now, and it was a fresh fill when I bought the place in Sep 2009. I drained and refilled in spring of 2012 since the CH had gone from ~250 up to about 1000. I figure it'll be an every 2 or 3 years thing. The less CH your fill water has, the longer you'll be able to go. I'm not sure what your CH is in Tucson (marana water here), but I think 4-6 years will be pushing it. Lots of people view scale as inevitable though...maybe that's why. Keep an eye on things and you'll be OK.