Converting Trichlor to Liquid Chlorine

JKB121

Well-known member
Jan 23, 2021
63
Pennsylvania
Pool Size
18000
Surface
Vinyl
I have been thinking about buying an injection pump (still researching) and eliminating the Hayward feeder. I'm interested to know if anyone has done this and could shed some light on the prospect. I'm not looking for exact scientific guarantees, just ball-park information.

We are too close to shutting down for the year so this would be a project next spring.

My details are:

27' round above ground, 54" high.
Approximately 18,000 gallons.
When my CYA is between 30 and 40 we are able to maintain 4-5 ppm FC.
Unfortunately, the Trichlor has added 100 ppm over the last 2 years. (the reason I'm thinking of switching)
I'll drain the pool in the spring and refill.
Currently we are maintaining 12 ppm FC. I'd like to get back to 4-5.
We used 50 lbs. of 1" Trichlor tabs this year. (cost about $200.00)
We heat the water to 87* in the spring and fall. (Pennsylvania Summer) It stays around 90* in the summer with a solar cover.
I'm wondering how much liquid chlorine I'd go through using a peristaltic pump. Liquid chlorine locally is 7.00/gallon (12.5%) to keep the FC around 4-5 ppm with a CYA level between 30 - 40.

Pump runs on low speed 24/7 except when heat pump calls for heat. Then it switches to high.

What I'm really trying to figure out is if this is going to double/triple my chlorine cost. If so, I'll just drain the pool every couple of years.
 

HermanTX

Gold Supporter
May 20, 2020
2,541
Katy TX
Pool Size
14600
Surface
Plaster
Chlorine
Liquid Chlorine
According to the PoolMath app, for 18kgals, 12.5% LC, 1 gal will raise your FC by 6.9ppm (say 7 for easy calcs).
Do you know how much FC ppm you lose a day during the summer?
For example if you lose FC of 3.5ppm per day then you will use about 1/2 gal per day of 12.5% LC to replace that. (trying to keep the math simple) So that is 3.5 gals per week x $7/gal is $24.50 per week.
You need to put in the right numbers but this will get you close assuming you have a consistent loss of ppm daily during your swim season.
Note - this excludes the LC needed to bring up the FC to your desired level based on your CYA. I only looked at replacement of daily FC loss.
 

Mdragger88

Bronze Supporter
Jun 1, 2018
2,968
Hernando, Ms
Pool Size
26000
Surface
Vinyl
Chlorine
Salt Water Generator
SWG Type
Intex Krystal Clear
Wow $7/gal? Here its $3.50-$3.99. Hopefully that’s just due to high demand for liquid right now because of trichlor being scarce. For me trichlor is much more expensive than liquid chlorine.
Pucks aren’t evil but they do have their downsides when solely used for daily chlorination as u have found. Most here that use them do so sparingly to increase cya a little or while on vacation.
So long as you’re aware of their effects on your chemistry you can use any form of chlorine as necessary to get where u wanna be.
PoolMath effects of adding can easily calculate how much liquid chlorine you would need daily to maintain proper fc levels for your pool volume as well as see the effects of other chems as well.
Most pools use on average 2-4 ppm/day.
Many here have done write ups on their stenner set ups. @Bama Rambler & @RonsPlc are in that club.
With the price of liquid chlorine in your area a swg would pay for itself in short order as well.

 
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GDN

Bronze Supporter
Oct 17, 2016
482
Dallas, TX
Rough estimate looking at my purchase records it looks like I've bought and used about 44 gallons of chlorine January to current. That is 10% and costs about $4/ gallon at Home Depot. My pool is about 11K gallons in TX so pretty good heat and sun in the summer.

I use a Stenner pump and really like the setup and have a write up here on the site, I've integrated it into my Pentair automation. Sometimes I think about Salt, but I had fun putting this setup together and learned a lot doing it, I don't regret it.
 
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JKB121

Well-known member
Jan 23, 2021
63
Pennsylvania
Pool Size
18000
Surface
Vinyl
Do you know how much FC ppm you lose a day during the summer?
For example if you lose FC of 3.5ppm per day then you will use about 1/2 gal per day of 12.5% LC to replace that. (trying to keep the math simple) So that is 3.5 gals per week x $7/gal is $24.50 per week.
With the kids only here sporadically now, we generally lose about 2-3 ppm/day on average. Some days the cover doesn't come off.
 

JKB121

Well-known member
Jan 23, 2021
63
Pennsylvania
Pool Size
18000
Surface
Vinyl
Rough estimate looking at my purchase records it looks like I've bought and used about 44 gallons of chlorine January to current.
We would "probably" use about half of what you use. We open up around April and will close in October.
That is 10% and costs about $4/ gallon at Home Depot.
My local Home Depot doesn't sell it, AND online it says cannot be delivered to my store...:(
use a Stenner pump and really like the setup and have a write up here on the site
I'd like to read this.... I'll search for it. I have no idea what pump or size to even start with. If chlorine is out of sight, I might be stuck with Trichlor or look into SWG.
 

GDN

Bronze Supporter
Oct 17, 2016
482
Dallas, TX
Update - forgot about my spreadsheet - it looks like I've been using about 28 oz per day during the hot summer months. I dial it back during the months it isn't as hot as we don't burn off near as much.

PS - the link to my write up is in my signature. And after seeing your reply - we stay open year round although we use very little chlorine Nov to March when the water stays below 60.
 

JKB121

Well-known member
Jan 23, 2021
63
Pennsylvania
Pool Size
18000
Surface
Vinyl
Update - forgot about my spreadsheet - it looks like I've been using about 28 oz per day during the hot summer months. I dial it back during the months it isn't as hot as we don't burn off near as much.

PS - the link to my write up is in my signature. And after seeing your reply - we stay open year round although we use very little chlorine Nov to March when the water stays below 60.
If chlorine is going to be around 7.00/ gal. it might just be too pricey. I'll have to shop around.
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,982
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
Liquid chlorine locally is 7.00/gallon (12.5%)
Do you have a Menards nearby? During swim season, they carry liquid chlorine for very reasonable prices.
 

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JKB121

Well-known member
Jan 23, 2021
63
Pennsylvania
Pool Size
18000
Surface
Vinyl
Do you have a Menards nearby? During swim season, they carry liquid chlorine for very reasonable prices.
We do not. I'm not sure they are in Pennsylvania. We are not far from Ohio, and I think they may be there.... worth a look! Thanks!!!
 

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,982
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
I know they have them in WV.
 

JKB121

Well-known member
Jan 23, 2021
63
Pennsylvania
Pool Size
18000
Surface
Vinyl
the link to my write up is in my signature
This is a great write-up. Exactly what I want to do..... If the chlorine price will be reasonable enough. Thanks for putting that together. I may have missed it.... what size pump are you using?
 
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JKB121

Well-known member
Jan 23, 2021
63
Pennsylvania
Pool Size
18000
Surface
Vinyl
I know they have them in WV.
WV is about the same distance. It looks like there is one in Morgantown. About a 45 minute ride.... Thanks!!

UPDATE: The closest Store in WV is 2 hours away. Is it the Pro-Chlor Pool shock? $3.55/gal ... better than 7.00! long ride though...
 
Last edited:

mknauss

Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
43,982
Laughlin, NV
Pool Size
6000
Surface
Fiberglass
Chlorine
Salt Water Generator
SWG Type
Pentair Intellichlor IC-40
I assumed you were near Pittsburgh and thus the Menards in Triadelphia WV. But am sure you can do the searching!

Take care.
 

JKB121

Well-known member
Jan 23, 2021
63
Pennsylvania
Pool Size
18000
Surface
Vinyl
PoolMath effects of adding can easily calculate how much liquid chlorine you would need daily to maintain proper fc levels for your pool volume as well as see the effects of other chems as well.
After tinkering with some hypotheticals on pool math, it may not be as bad/expensive to maintain my FC after all.
 
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GDN

Bronze Supporter
Oct 17, 2016
482
Dallas, TX
This is a great write-up. Exactly what I want to do..... If the chlorine price will be reasonable enough. Thanks for putting that together. I may have missed it.... what size pump are you using?
I bought a 45mphp10 from Lockwell.com - one of the better prices I found a few years back. I wanted one I didn't have to overwork for the amount of chlorine I needed. During the summer I average 30 to 40 minutes a day as I adjust it through out the season.

I've done testing with mine and it pumps about 1.1 oz per minute.
 

JKB121

Well-known member
Jan 23, 2021
63
Pennsylvania
Pool Size
18000
Surface
Vinyl
I bought a 45mphp10 from Lockwell.com - one of the better prices I found a few years back. I wanted one I didn't have to overwork for the amount of chlorine I needed. During the summer I average 30 to 40 minutes a day as I adjust it through out the season.

I've done testing with mine and it pumps about 1.1 oz per minute.
Since you've already done this and it works, what do you think about this. I spoke with a Stenner tech support guy today who seemed very knowledgeable. Since I run the filter pump 24/7 I'm okay with feeding 24/7. He suggested a Low Dose pump that ranges between .11 and 8.1 oz. per day. He figured an 8 setting should maintain 3 ppm per day. His logic on a bigger pump was that unless I wanted to run a timer, choking it down is harder on the pump. (seemed logical). I don't know how large of a tank I would need, so I'm thinking 15 gal.
 

GDN

Bronze Supporter
Oct 17, 2016
482
Dallas, TX
The Stenner guys are good and there is one that used to even visit and post here on the forum. I'm likely just old school and believe the less a motor runs the longer it might last so I didn't want to run one at all times. I also vary my pool pump throughout the year. Winter maybe only 6 hours a day, summer up to 10. I wanted to control my chlorine flow with an independent timer and likely my biggest factor was that I also had a relay available on my Pentair controller and knew I wanted remote access. Also I've been through times I ran out of chlorine or had bigger groups of people in the pool, I wanted to just hit a button and give it an extra days worth. If the pump is already pumping near its max you won't be able to get that extra boost by just turning it on for 30 minutes.

I also truly don't recall what it was, but I was thinking there was something that turned me off about the variable flow pumps. I can't recall what it was, maybe they way they adjust or have more parts, I don't recall. I just wanted to stay with the simpler pump.

I also think 15 gallons at a time is more than you need. I've got the 15 gallon barrel, which is perfect for me. I've never filled it. The most I've ever put in is 12 gallons.
 

JKB121

Well-known member
Jan 23, 2021
63
Pennsylvania
Pool Size
18000
Surface
Vinyl
Oh My... More to think about!!

Using your logic, I could use My SmartThings hub to control a Zwave outlet to control a pump like yours. I can control an outlet down to seconds, and with a touch of a button, turn on extra CL.

So maybe I was thinking along the lines of my Trichlor feeder that feeds all day. I was thinking feeding only a few hours out of 24 would cause peaks and valleys in the FC where a steady feed results in more consistent FC. Is that bad logic?
 

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