Chlorine guidance sought

[Coconuts]

Hi; I just joined, and while I have spent some time reading through forum posts and educating myself, I have some special circumstances, and would appreciate some advice on the best way to maintain FC levels.

I have three pools, one 20' x 40' in New England, and two much smaller 12' x 18' pools on St. John, in the U.S. Virgin Islands. This post is focused on the two smaller pools. Both homes are short-term rentals, and nearly fully booked year-round. They get weekly service by pool maintenance guys, but I have concluded that their approach to pool chemistry is all wrong. They mostly use tri-chlor tabs, but since there is no winter drain down, the CYA levels are off the charts, which also requires very high FC levels. I recently bought a Taylor K-2006 test kit, but I would have to dilute the pool water to even get a reading on the Taylor test.

It would be nearly $500 per pool to dump the pool water and start over, but I am considering doing this. I like the bleach, baking soda, and borax approach. The only intervals for pool service are weekly, so if the FC levels would drop too far during a week, some automated way to add chlorine would be needed. A mid-week service visit is another option, but that would be pricey. While the pools are small (6500 gallons), it is very sunny, and we use solar pool heaters to keep the water temperature in the low to mid eighties. Electricity is expensive (52 cents a kW-hr), so I use a variable speed Pentair pump set to a fairly low RPM (1500). I have flow meters, and this pump operating from 9:30 AM to 4:30 PM (when the solar heaters receive sun) is enough to move all of the water through the filter once each day. I am aware of SWG's, and while a small one wouldn't use that much electricity, they would lower pH, and appear prone to technical issues that the local pool guy would not be able to diagnose or address.

My questions are as follows:

Would a once a week application of liquid bleach work, or would some more frequent delivery method be necessary?

What daily decline in FC levels should I expect?

Could a once a week application of bleach or liquid chlorine serve as a shock, and still have enough FC level left one week later?

Would an increased level of CYA help in this case? I see recommendations of 40 ppm. What level would work best?

Is there any anti-algal value to adding salt in the absence of an SWG?

Should I hook up a peristaltic pump and add liquid chlorine that way?

Or should I use an SWG and simply plan on regular replacement of the cell before it can decline in effectiveness?

Thanks in advance!

Kevin

 

[karmabiker]

My questions are as follows:

Would a once a week application of liquid bleach work, or would some more frequent delivery method be necessary?

No - you will need a more frequent delivery - daily at minimum.

What daily decline in FC levels should I expect?
Veries by the pool and bather demand and what level you start at. Starting with a swimmable level on day 1 you would likely be near 0 on day 3.

Could a once a week application of bleach or liquid chlorine serve as a shock, and still have enough FC level left one week later?
No - reread pool school and familirize yourself with the SLAM process. (Shock Level and Maintain)

Would an increased level of CYA help in this case? I see recommendations of 40 ppm. What level would work best?

40 is ideal with stenner delivery.

Is there any anti-algal value to adding salt in the absence of an SWG?

Not to speak of.

Should I hook up a peristaltic pump and add liquid chlorine that way?
This or SWG. Given the remote nature of rental properties SWG is probably better (Personally I am a big advocate of Stenner and liquid chlorine, in your case SWG is a winner)

Or should I use an SWG and simply plan on regular replacement of the cell before it can decline in effectiveness?
See above - SWG looks like the way to go.

Thanks in advance!

Kevin[/QUOTE]

 

[Isaac-1]

The big problem with automated chlorine delivery, either SWG or liquid Chlorine pump is it only handles one side of the equation, delivery, you still need testing to know if your reaching your goals, and neither testing nor dosing can effectively stretched out to a weekly event. At a minimum I would consider twice per week testing and adjustment of an automated delivery system, in the case of either an SWG or Chlorine pump, having a easy to swap out spare on hand may be the best solution to limited skills pool people. Some of the SWG's one the market have a screw out cell that can be changed out in under 5 minutes with no tools. Any attempt at once per week dosage and testing by a pool service is bound to result in a roller coaster of chlorine levels swinging from insanely high to insanely low resulting in unhappy swimmers, chlorine smell, red eyes, etc. Having said that the public has learned to accept such things as normal, we here tend to be a lot more picky.

 

[bobodaclown]

Chlorine injection system might work for you.
Some links: http://www.troublefreepool.com/thre...-on-my-proposed-Stenner-solution-Completed!!?

http://www.troublefreepool.com/threads/56434-Why-chlorine-injection?

Once a SWCG is "dialed in" they're pretty maintenance free.

Go large on the cell it's worth the money spent.

 

[Coconuts]

Thanks to all for the advice. I guess I will go with an SWG and as suggested, keep a spare on hand. Can I leave the SWG (Pentair) plugged in and the pool pump flow will automatically enable the SWG? I run a Pentair Intelliflo pump at modest RPM (1500, ~ 30 fpm if my flow gauge is reading correctly). Perhaps the pump can interface directly to the SWG, but I would like to avoid the complexity of a separate automation controller.

Kevin

 

[Coconuts]

Decision made. It turns out that a supply company on the neighboring island offers free delivery to St. John, and they sell a 55 gallon plastic barrel with 10.5% sodium hypochlorite solution for $210.00. I purchased a Rola Chem RC-25/53 SC, along with a digital timer. The liquid chlorine barrel shows up tomorrow morning, and the pump and timer were installed today. No changes to CYA, calcium, or pH levels, daily chlorination, and the 55 gallon barrel should last for over a year. Assuming that it works well, I will duplicate this at our next door property. The one remaining decision will be to discard the pool water (which has really high CYA levels), and start over. Water is 8-10 cents a gallon here.


All the best,

Kevin

 

[Isaac-1]

The only problem there is shelf life after a year in warm weather that 10.5% will likely loose enough strength to be more like 3 or 5%. I will help if you can store it in a relatively cool dark place. In the future you may be better off with a 15 or 30 gallon drum and changing it 3 or 4 times per year.

Ike

p.s. here is a half life chart http://www.odysseymanufacturing.com/about_product.htm

and a link to more talk about liquid chlorine aging http://www.troublefreepool.com/threads/26383-Does-liquid-chlorine-go-bad


One more p.s. do we get a discount if we agree to tune up the pool water while we are there?

 

[jblizzle]

As Isaac said, that chlorine is going to get awfully weak by the end of the year, so you may have to continually play with the dosage.

I pay 8 cents per 100 gallons of water ... you are going to have a very hefty bill getting your CYA in check.

 

[emlowe]

Just my experience, I had my CYA go from 100 to 0 in one calendar year once I stopped putting in trichlor. Evaporation turnover and rain dilution shouldn't be discounted if you are in a hot dry climate. I read this from a City of Scottsdale AZ website: "It's estimated that a 400 sq. ft. pool will lose approximately 19,665 gallons of water per year to evaporation."

So if you have an auto-fill, you may be turning over your pool already without knowing it. You could do a bucket test to see how much you will lose.

 

[jblizzle]

CYA does not evaporate. Evaporation and adding back in water will not lower the CYA level. It is only lowered when you physically remove water from the pool (backwashing, splashout, leaks, etc) ... and sometimes the CYA is lost over the winter in a closed pool.

 

[Coconuts]

Thanks for the comments; the decomposition is important, and I didn't know about it at all. I had assumed that all I needed to do was keep the container tightly sealed. We will be keeping it in a closed garage which probably averages 75F; at 10.5%, a chart at Issac-1's link indicates that the time to half concentration is about one year. We have a second home on this hill which I plan to convert to liquid chlorine, so one option would be to split the 55 gallons of 10.5% between the two homes, and dilute each barrel 2X to ~ 5%, which appears to triple the half life.

Thanks again for the valuable posts. As much as I wish that the CYA level will drop of its own accord after we stop adding tablets, I suspect that an expensive dump and refill will be required to really control the pool chemistry. My local pool guy was unaware that FC levels depend on CYA levels, which may be why our pool isn't crystal clear. With sky-high CYA levels (300+), the FC needs to be really high as well.

All the best,

Kevin

PS: That plug was in violation of forum rules; got it.

 

[emlowe]

It was my experience that it went down. I shouldn't have attributed it to evaporation. But it disappeared in some fashion without me explicitly draining the pool. My water is metered and I would know quickly if I had a substantial leak.

 

[Isaac-1]

CYA does break down, but very slowly unless you have swamp like conditions, in hot tubs with 100+ degree water it happens somewhat faster at a rate around 5% per month

 

[Coconuts]

The 55 gallon plastic drum of 10.5% bleach arrived last week, and I also bought a second empty drum. A local firm performs a second reverse osmosis process on town RO water for drinking water gallon jugs, so I bought 54 gallons from them and diluted the bleach 2:1 in the two barrels. In my dark covered garage at about 75F, this should have a half life of three years. I installed a Rola-Chem RC 25/53 peristaltic pump, and a Woods digital timer with battery backup that injects bleach into the main feed lines once a day while the pump is running. It was expensive, but I dumped the pool water and started with reverse osmosis water from a high-end hotel's system. I then added the right amount of dry chemicals to set levels. I am pretty encouraged that this system will work very well, and barring any surprises, will clone it next door at our other property. I used my Taylor K-2006 to dial in all other parameters (TA=100 ppm, CH=270 ppm, CYA=60 ppm, and pH =7.5). I left island this weekend, but my pool guy will be monitoring FC levels twice a week, and adjusting the knob on the Rola-Chem until he hits the right amount of bleach to replenish the FC level. I appreciate all of the help, and have learned a LOT about pools in the last few months!

All the best,

Kevin