Rain water to lower CH -- pros and cons

dntboles

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Jun 29, 2019
76
Boerne, TX
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I'm considering using rain water to lower our CH and I'm looking for pros/cons.

Our pool CH is 375 and fill water is 150. I'm watching pH closely to prevent scaling but would like to keep the CH nice and low.

As I drank coffee and watched the water flow out the downspouts this morning, I thought about running some of that water (when I choose to -- not always) into the pool to lower the CH. But I'd like to get y'all's thoughts on that.

When I backwash, I take my time, to drain out more water and refill with fresh water, but with 150 CH fill water, it isn't going to impact much. But using a little rain water at 0 CH might help. I can manage pH, chlorine, TA with chemicals but don't have those same options with CH.

Thanks for your help.
 

Texas Splash

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Jun 22, 2014
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Those were some crazy storms this morning right? I like to take advantage of fresh rain every chance I can. It's best to lower the pool's water level in advance then let the rain fill .... IF/WHEN the weather predictions are correct. :hammer: Some people will also use rain barrels to collect water for future use.
 
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HBrittan

Silver Supporter
May 9, 2020
45
Benbrook, Texas
That's a good question. I was wondering the same thing. We are farther north than you but we got over 2.5 inches last night and I had to pump the level down this morning because it was over the skimmer. We just finished SLAMing our pool and are leveling things out, so it is interesting to see how variables other than chemicals affect balance.

I don't have any technical advice. Mostly I wanted to say I liked your A&M Icon.
Gig 'Em '92
Harry
 
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Richard320

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LifeTime Supporter
Jan 6, 2010
23,933
San Dimas, CA (LA County)
I've done it.

First thing is to let some of it get away. The roof collects a lot of dust and it will all end up in your pool unless you let it rinse well.

I stretched a knee-high nylon across the downspout to catch the shingle grit.

I run the water into my spillover spa and let that act as a settling basin. It can get pretty dark and evil looking, but running it through the filter in spa mode foxes it in minutes.

You'll have to figure out how much area drains and how much water you need to make room for. For me, it's about 3X the surface of the pool. So if the weatherguessers say an inch to an inch and a half overnight, I know I;m looking at 3 to 4 inches.

Besides lowering CH, you'll lower CYA the same amount. And TA.
 
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dntboles

Well-known member
Jun 29, 2019
76
Boerne, TX
Pool Size
15818
Surface
Plaster
Chlorine
Liquid Chlorine
Here's my connector. It's a short flex-a-spout to easily put on the gutter, a PVC connector and a hose clamp. We have PVC left over from fixing the irrigation system after the pool dig.

I thought I had replied before, but must have stopped before posting. We have an overflow pipe, so the water can't go higher than that. We will also use the nylons to filter out some of the sediment.

This is a very temporary thing, primarily for lowering CH. We will just connect it when we expect extended rain, so ease of storage is important. Per pool math, once I've captured 7,400 gallons I'll be good! ;-) IMG_5217.jpg
 
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dntboles

Well-known member
Jun 29, 2019
76
Boerne, TX
Pool Size
15818
Surface
Plaster
Chlorine
Liquid Chlorine
JUST after I clicked to post, it started raining. It started light, then picked up. Right now it's medium-heavy and it's easily coming out at 5 gallons per minute x 2 pipes. And we didn't have rain in the forecast and already have 1/2" of rainfall.

Tomorrow, it is supposed to rain, so I'll backwash some extra out of the pool and let the rain fill it back up.

Rain water (coming off the roof) pH is 7.3. CH went from purple initially to deep blue in 1 drop, so way under 25.
 
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