Reducing CH via Rain

[MattM]

Been awhile since I've last had to post, however the next pool season is almost here and our pool's CH has just crossed 500....and I checked the weather for this weekend, looks like almost two days straight of rain....and it's already started.

Can I just open the auto cover and let new rain splash old water out via our the built in overflow protection and reduce CH noticeably that way? No, I'm not that adventurous to pump out the water in advance. Our pool is almost always covered and CH goes up 10-30 pts/month due to the local tap water being imported hundreds of miles. Alternatively, it appears that I'll end up having to get reverse osmosis performed every February...

 

[Bama Rambler]

Richard 320 has taken CH adjustments to a whole new dimension. He uses rain water to reduce the CH in his pool and is very good at it. What you propose might work to lower it some, but pre-pumping the water off would be better as you wouldn't have "mixed" (rain & high CH) water going out the overflow.

 

[jjslinger]

I notice you have an automatic cover, as do I. What I have been doing is keeping the cover closed during rain, and using the cover pump to pump the rain that collects on the surface of the cover to the end of the pool opposite the overflow; my reasoning is that most of the water that goes into the overflow will be "old" water, and the "new" rainwater will be mostly retained. This has a side benefit that there is some amount of filtering of the rainwater with the cover pump, and helps to keep the pool water somewhat cleaner as new water is introduced. However, I'm not as desperate as some since my fill water is half decent (CH=140), I just think that using free rainwater in the winter for replacement is a good idea. If you want to get every drop of CH-free rain, I think you need to do the pre-pumpdown, as mentioned.

 

[Richard320]

The water level in my pool fluctuates normally between additions, so I just pump it down to the low level before a rain and hope for the best. I also have the downspout directed into the spa, where it acts as a settling basin. It's easy to clear with the valves set spa in, spa out after the rain stops.

 

[MattM]

I guess the question is how much new water do I get with rain.....yes, that will depend on the weather and location.....we don't get a huge amount of annual rainfall here in San Diego, but we get at least a few days non stop here and there during the rainy months....even if I pumped out water, it's unclear how many gallons we're talking about.......I think total yearly rainfall is 10 inches all precipitation combined and in a good storm, maybe 0.5-1 inch at best...assuming I can collect 2.5 inches at best a year, does that turn into anything that noticeably delays needing to replace the existing water..I'm worried not....but I'm still looking for any quantifiable examples from others.

 

[Richard320]

I guess the question is how much new water do I get with rain.....yes, that will depend on the weather and location.....we don't get a huge amount of annual rainfall here in San Diego, but we get at least a few days non stop here and there during the rainy months....even if I pumped out water, it's unclear how many gallons we're talking about.......I think total yearly rainfall is 10 inches all precipitation combined and in a good storm, maybe 0.5-1 inch at best...assuming I can collect 2.5 inches at best a year, does that turn into anything that noticeably delays needing to replace the existing water..I'm worried not....but I'm still looking for any quantifiable examples from others.

Quantifiable, you say?

Well... the area of the roof that drains into the pool in my case works out to about 3X the surface area. One inch of rainfall will give me 3" in the pool. My average depth is 60". So... one inch of rain will lower my CH about 5%, which is nothing to sneeze at when CH is running around 800. If I got 10" and I did everything perfectly, I'd lower CH by 50%. But it's an imperfect world. Still, it's free water.

 

[jjslinger]

Based on measurements, my system is about 40% effective; we have had 13 inches of rain this season, and my CH has dropped from 300 to 275, which means it's behaving as if it got 5 inches of replacement water. I haven't been 100% diligent; for small storms (less than 0.5 inch) I haven't bothered to set up the cover pump, I just use the automatic cover to shift the small amount of water off.

 

[MattM]

Thanks for the info! I assume TA reduction would also be a nice bonus. I'll give it a try for big storms going forward and try to collect my own data.