Reverse Osmosis Treatment vs Drain & Fill

LeviStraussTx

Member
Jul 30, 2021
22
Fort Worth, TX
Pool Size
14000
Surface
Plaster
Chlorine
Liquid Chlorine
I recently fired my pool service and started taking care of my own pool. The biggest reason I got rid of them was because they kept telling me everything was fine, and every time I tested the water, I had nearly zero chlorine and my skin felt super dry. I had used some test strips and Leslie's (forgive me) spin test, and they all say my CYA is well over 100, sometimes 150+.

I bough the TF-100 test kit and did the full spread of tests, and the two huge outliers are that my CYA is over 100 (test kit only goes up to 100) and my CH is over 1,625. This helps explain why I feel so gross when I get out...it's super hard water. My first thought was to drain and fill, but it's over 100 degrees daily and rarely below 80 at night, and I don't want to crack my plaster/pebble finish. The other downside is that I measured my tap water, and it was in the 500-600 range (I tested it 3 times and got 500, 550, and 600). My other thought was to do a Reverse Osmosis treatment. In talking to the guy that does the RO treatment, he said with my current levels, he could probably only get it to about a CYA of 30 and a CH of 500. The CYA level of 30 is probably perfect since the pool gets full sun all day long in North Texas. But the CH at 500 wouldn't be any better than just using tap water to refill it.

My question is this: Is there a safe way to do a full drain & fill with the temps being in the 80-105 range daily? Are the levels so bad that I need to address it immediately? Can it wait until it cools off and do the drain & fill in October? I can't refill from Nov-Feb, as they use the average water use for those months and that determines your sewer bill for the next year. I really don't like having the CYA that high, as having Chlorine levels high enough makes it an unpleasant experience. But at the end of the day, it's better than no pool when it's this hot outside.
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
18,798
Tucson, AZ
Pool Size
16000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Do the “exchange drain” that’s outlined in the Wiki article that @mknauss posted. I recently did that back in May and I was able to get my water from 1150ppm CH to about 550ppm. It took 2 days to exchange out 11,000 gallons of water. You will notice the subjective difference in the feel of the water when you get the CH down.

Also, I would suggest you get a whole house water softener installed with it plumbed out to your auto fill or an outdoor spigot. Your municipal fill water is too hard.
 

LeviStraussTx

Member
Jul 30, 2021
22
Fort Worth, TX
Pool Size
14000
Surface
Plaster
Chlorine
Liquid Chlorine
As far as a water softener, that would be tricky. The pool auto fill is run off of the irrigation system. That system splits off of the mail water feed at the front of the lot with one branch for irrigation and the other going to serve the house. Thus, in order to soften the auto-fill it would have to be a dedicated system just for the pool.

As for a whole home softener to get soft water out of the hose bibs, that’s not really an option either. The water main comes into the slab at the front (guest) bedroom and then splits off to all of the different feeds throughout the house from within the slab.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
44,835
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
So you have 600 ppm CH tap water and no whole house water softener? How fast do your appliances scale up?
 

wireform

Silver Supporter
In The Industry
Aug 15, 2017
3,305
Spring Valley, NY
Exchange drain works well as long as all parameters are considered. Did one about 6 weeks ago although it was a vinyl pool it took 2 days as per calculation but in the end it was almost spot on. You need to exchange a little more for insurance so you're not left with " oh should have drained more or need more" kind of thing.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
44,835
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
For the exchange drain how should you determine TDS?
TDS in a pool is primarily salt and calcium. CYA adds a little. If you do not have a salinity test, assume your pool water has 1000 ppm. Your tap water will have about 200 ppm, or so.
 

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LeviStraussTx

Member
Jul 30, 2021
22
Fort Worth, TX
Pool Size
14000
Surface
Plaster
Chlorine
Liquid Chlorine
So you have 600 ppm CH tap water and no whole house water softener? How fast do your appliances scale up?
Shower heads get crusty after about a month, then they need a vinegar soak. Dishwasher has a built in softener. Coffee pot, washing machine, and dishwasher all get cleaned with Affresh monthly. Steam oven gets cleaned with Durgol cleaner about every 6 months, and the water heaters get flushed every 6-12 months.

I never really thought too much of it, just part of taking care of equipment. But now that I’m writing it down, it seems to make sense that hard water could be to blame. I looked up our city water report and it reports total hardness as CaCO3 at 112-160 ppm And total hardness in grains as 7-9 gpg. There‘s a house under construction down the street and they have a hose bib coming straight off the meter. I’m going to go take a water sample from that just to validate my tap water readings from inside the house. Something seems off if the city report is saying 112-160 ppm and I’m reading 500-600 ppm.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
44,835
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
We have 16gpg water, no whole house softener, and that laundry list of items you have to do, I do none of. Interesting.
 

LeviStraussTx

Member
Jul 30, 2021
22
Fort Worth, TX
Pool Size
14000
Surface
Plaster
Chlorine
Liquid Chlorine
So, I did some more testing. Tested the pool water, hose bib next to the pool that I would use for a fill hose, and the water straight off the meter at the house next door.

Pool CH is now 1225. I tested it 3 times to validate my numbers. I must have mis-counted last week when I was doing the drops.

Hose Bib CH is at 425-450, so pretty close to what I was reading out of the garage utility sink last week. Interesting enough, it has 2ppm chlorine, which is good news for getting the pool back up and running after replacing the water. pH is at 8.2 and TA is 130. All good news, other than the fairly elevated CH.

Water @ Neighbors Meter CH is at 375.

With my hose bib and the water meter about 50 ppm apart, I think that’s fairly reasonable. Seems like maybe I’m getting a little higher reading at the bib since it’s more stagnant Sure if that’s reasonable logic or not. I’m hoping that if I’m running it for hours on end, it’ll clean up and be closer to the numbers from the meter sample I did.

For the in-place water replacement, I’m thinking I should be filling new water into the deep end down low, and pumping out old pool water from the shallow end up high. Planning to place the submersible pump on the sun deck so it’s in the top 3-6 inches of water. Pool water is about 86 in the morning and 90 at the end of the day lately, with TDS of 800. New water is about 78 degrees. I didn’t test it for TDS, but the city water report says ~250. The math I get is a positive number above 5. Does this all sounds right?
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
44,835
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Have you done the calculation shown in the Wiki article using TDS and temperatures of the two waters?
 

C3Cl3N3O3

Bronze Supporter
May 25, 2015
327
Fort Mill, SC
I'm impressed Leslie's alerted you to the high CYA. My pool store told me I was "good to go" with a CYA of 100. Of course, as you say, the test maxes out at 100. In reality I was closer to 200. You can test a solution of 50% distilled water / 50% pool water if very high CYA is suspected.

They use the same reagents as the rest of us and will certainly alert you to low CYA (cha-ching!)
 

JoyfulNoise

TFP Expert
Platinum Supporter
May 23, 2015
18,798
Tucson, AZ
Pool Size
16000
Surface
Plaster
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-60
Wow. A 375ppm CH (~ 22 gpg ) municipal water supply is terrible. Given the high pH and TA, it’s no wonder you’re having to vinegar soak all your fixtures every month. The CSI of the incoming water supply is +0.9. I’m surprised your municipal supplier is delivering water like that, it must scale their equipment too. Usually they try to aim for slightly positive saturation, maybe +0.1 to +0.2. +0.9 is ridiculous.

You should consider talking to a water treatment company or a plumber that installs water softeners to see if they have any good options for you. There’s way too much hardness in that water and you’ll be draining your pool every couple of years to simply keep the water at the high end of recommended levels.
 

LeviStraussTx

Member
Jul 30, 2021
22
Fort Worth, TX
Pool Size
14000
Surface
Plaster
Chlorine
Liquid Chlorine
Thanks for all of the advice. Mother Nature decided to cool off and rain for the weekend, so I called an audible and just did a full drain and fill to start all fresh. I got up around 2am to check on it and it was about an inch away from full, so I shut off all the hoses. Today I’ll start it up and start getting it all balanced. I’ll post some pictures later on.
 
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