High calcium hardness

[Dwiessner]

My pool is fiberglass, 18000 g. Calcium hardness is 975. My Tap water has a hardness of 275. Just bought a sump pump and plan to drain some pool water before socal gets drenched with rain later this week. What is a acceptable ch range, and how much water should I drain to reach the high end of that range?

Water here is about as expensive as crude, so I'd like to drain the minimum I can.

 

[mknauss]

I have 250 ppm CH fill water and very high evaporation. Luckily, our water is very inexpensive. I manage my CSI until the CH gets to 900 or so. Then drain and refill.

If you are unable to drain and refill with fresh, then do as much as you can. And manage your water using CSI which is calculated in PoolMath

 

[JoyfulNoise]

I recently added a whole-house water softener and ran a connection out to my autofill. Now pool only gets 0ppm CH fill water whereas my old fill water from the city was around 200ppm CH. My CH has been as high as 1500ppm but I would recommend not trying to manage water that hard, it’s a pain. @mknauss is spot-on, once you get above 900ppm, best to drain and refill.

 

[Dwiessner]

Thanks. Full drain, or can I get away with doing 50-60% for now?

 

[Texas Splash]

Us FB owners should never risk a major drain at the risk of having the shell shift or worse yet pop-up. Even though I doubt you have a high water table in your area, I personally wouldn't go any more than about 30 at a time - 40% at most. Now some folks might try other methods like pumping-in new water while simultaneously removing water, or even what's called a tarp method. But given the high cost of water in your area, even a little at a time is better than nothing at all. Remember to watch your other levels (i.e. FC/CYA) as you exchange water.

 

[YippeeSkippy]

Over time if you know you'll be getting a drenching rain, drop the water level an inch or so each time. Then let the rain refill you. This is just one more way to fight back against high CH fill water and evaporation which takes water but leaves calcium.

I only ever recommend fiberglass owners drain no more than 20-30% at a time and refill *immediately* as the water inside the pool helps maintain the pressure on the walls outwardly. Fiberglass is never meant to be emptied without professional assistance. In less dry climates they often include a large PVC drop down point which allows you to monitor ground water under the pool itself and remove if necessary.

Maddie

 

[mknauss]

Issue with only a partial drain is your CH will only drop a fraction. Later I will post a water exchange method you can look at.

 

[mknauss]

You can exchange some water without draining.

If you place a low volume sub pump in the deep end and pull water from there while adding water in the shallow end (through a skimmer or into a bucket on a step so you lessen the water disturbance) you can do a fairly efficient exchange. That is assuming the water you are filling with is the same temperature or warmer than your pool water. If your fill water is much cooler than your pool water, then switch it. Add the water to the deep end (hose on bottom) and pull water from the top step.

The location of the pump and fill hose may change if you have salt water, high calcium, etc.
In my pool, with saltwater and high calcium when I drain, I put the pump in the deep end and hose in shallow end. The water in the pool weighs more per unit volume than the fill water from the hose.

Be sure to balance the water out and water in so the pool level stays the same. Also be sure your pool pump is disabled during this process. Once started do not stop until you have exchanged the amount of water you wish.

The issue with a partial drain, say 50%, your resulting CH will still be well above 600 ppm. Which will mean you are back were you are now by the end of this summer.