Frist reading from TF-100

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tjwill

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Feb 27, 2011
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Got my test kit and took my first readings. First a little background information. We will be doing SWG, but during the break-in period, the PB's service guy had me do a shock and added 4 tablets 3 days ago and then I'm to do another shock after a week. He added sequestrant, CYA, and some dry acid. I've added some additional dry acid based on pH readings from the test strips he gave me. Here are the readings from the TF-100:

FC - 0.5 (I would say the reading was probably a little higher than 0.5, but not 1.0)
CC - 0.0
pH - 7.5
TA - 100
CH - 110
CYA - 20

It looks to me like my chlorine levels are dropping very quickly, which makes sense since I have very little CYA and full sun all day long. I didn't understand his double shock approach, but now I think I do. He doesn't want to waste his time teaching me how to control the chemistry using chlorine when I'm going to be switching to the SWG anyway. He probably wasn't sure how long the chlorine from the shock would last, but the assumption is that any problems that develop after the chlorine is gone will be killed by the second shock. I'm not comfortable with this approach because I can practically guarantee that the PB won't be out to start up the SWG for 3 weeks. I'd rather actually be in control of the chlorine level.

I plan to add bleach tomorrow, but my question is whether the second shock makes any sense or does my assumption sound correct? Any guidance on how much bleach to add would be appreciated. The pool is about 27,000 gallons. I don't mind adding slowly and checking it as I go, but I'm not sure whether to start with a quart or 3 gallons.

Also, based on these readings, is there any preference for dry acid or MA? I have some of both on hand, but was planning to use MA long term.

Thanks,

Tom
 
How old is the plaster? For fresh plaster you want to be very cautious about adding too much chlorine in the first week or so. The usual routine is to use trichlor tablets continuously with the pump running 24/7 for the first three or four weeks. If you do that, low FC levels in the afternoon/early evening are just fine.

It would be a big help if you put some basic specs in your signature, and keep the discussion together in one place so we have some context of what has gone before.
 
Shocking isn't a one time thing, it's a process of maintaining a FC level high enough to kill the organics in the water. I would recommend bringing your CYA up to 30 using stabilizer (100% Cyanuric Acid) and then adding enough bleach to reach shock level, which for a CYA level of 30, is 12. Keep it there until your water is clear, you have a CC of less than .5 and you pass the overnight FC loss test. After that, I would bring up the CYA level to 70, calculate the amount of salt you need (using the SWG read or our a salt test if you have one) add it, wait 24 hours, with the pump running, and crank up the SWG.

If you think there might be issues with your pool guy by doing the later on your own, I would just maintain FC with bleach (according to the CYA chart) until he returns.
 
Thanks, and yes, it is a new plaster pool.

Jason, I wasn't sure if it was better to separate the topics or keep it together, but I'll keep a single thread in the future.

The plaster is 8 days old. The plaster was done a week ago Friday, the pool was filled Saturday morning, the service guy came out on Tuesday to start the pump and add the chemicals he put in, then I did the first shock on Wednesday evening.

The service guy didn't seem too worried about too much chlorine. The dose used for the shock was in excess of the recommendations on the bag. I only had the test strips at the time, so I can only say it was above 10ppm.

When I was buying some CYA, the pool store told me that they don't add it in the first month for a newly plastered pool. I knew my service guy had added some, so I appreciate any input on target CYA levels at this point.
 
Re: First reading from TF-100

OK, I'm going to maintain my chlorine level with bleach and only do the second shock if my FC/CC readings indicate it's necessary. I was thinking of waiting another couple days before adding any CYA in case the reading isn't accurate, yet. It looks like I should also start adding Calcium Chloride to bring my CH reading up slowly.

I'll keep you posted.
 
It is too soon to work on CH. Fresh plaster will raise PH, TA, and CH levels fairly quickly for the first three or four weeks. Don't worry about TA or CH until it has been three weeks. If you adjust them now they will then go up and end up too high.
 

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