To SLAM or not to SLAM?

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VinceT

0
Aug 21, 2013
11
New Hampshire
I became a new pool owner last summer. I was fortunate to find TFP from the get go and was able to have a truly trouble free pool for my first partial season here in beautiful southern New Hampshire. As I am ready to open my pool for the first time and, after a long and heavy snow season, I am starting to think about the intricacies of pool maintenance. I tested my water for the first time just this evening. My testing has now left me with many interesting questions, perhaps too many to tackle in this single tread. I will post my results and a few queries and, if need be, will post other questions on a different tread.

I lifted part of the safety cover and was pleased to see that, except for a relatively small amount of leaves, the water looks good and I can see the bottom of the pool quite well. It was a very heavy snow season and my water level is now above the skimmers. It was closed by the people who built the pool with, I presume, partial drainage of the water below the skimmers...so, no doubt, some dilution from precipitation.

Test kits; TFTestkits TF-100 (FAS/DPD), AquaChek Test for Salt strips, Insta-TEST Borate strips.

Results;
pH - 6.8 current, (7.7 at closing)
TC- 0 (5.5 at closing)
CC - 0, (0 at closing)
TA - 10, (70 at closing)
CYA - 0 (70 at closing)
CH - 20
Borate - about 10 or between 0 and 15, hard to tell, (about 80 at closing)
Salt - test strip = 1, where lowest reading on chart is 1.8 = 370, (6.8 = 3460 at closing). So almost no salt!

So, here are a few of the questions I hope some of you might enlighten me on:

1) It makes no sense at all that my salt concentration is near zero. There has been no recent heavy rain; is it possible that I sampled surface "fresh water" and that there is a halocline separating it from deeper salt water? If so, it could explain all of my other unexpected test results. However, I would have expected that, by now, everything would have equalized by diffusion. I plan to start my pump this weekend, if I can find the time to get everything ready, and retest once things get mixed up.

2) If I have zero chlorine and zero CC, does that mean there is no algae/bacteria/organic material and, therefore, I don't need to SLAM the pool? There are plenty of leaves in the pool, so there must be some breakdown I would think. Is it possible that there is no CC simply because there is no chlorine to bind with "stuff" to form CC's and they will form only after I add chlorine?

3) Bonus question; is there a difference between shocking and SLAMing a pool. I haven't been able to find any posts on this, I hope not too silly, question.

Anyone interested in tackling this? Any input would be much appreciated!

Vince
 
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Welcome Vince.

Did you run the filter before you tested the pool? If not, do so and re check your test results.

The word *Shock* makes people go crossed eyed and confuses them. Most people feel like they can purchase a bag of shock and say, I *shocked* my pool. If you want to get technical, Shocking and SLAM'ing are the same thing as long as we're on the same page and doing it the same way in which we're raising FC to shock levels and maintaining it. Oh looky. there is that SLAM word!

SHOCK
LEVEL
And
MAINTAIN

SLAM. :goodjob:
 
What he said ^^

You wouldn't treat the water without it circulating, why would you test it without it circulating?

The only way to be absolutely sure you don't need to SLAM would be to run an overnight chlorine loss test. Myself, I think I'd just let the water mix, adjust pH/TA, and then take it up to SLAM level. Then run the overnight test after it's had time to mix well. If you didn't need it, you're only out a few bucks for the extra bleach, but if you did, you've got a day's head start on the SLAM!

Almost forgot to say Welcome :wave:
 
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Thanks Casey and Richard. I tested without circulating only because I just lifted part of the safety cover to get a first look at the pool. I haven't yet had time to commit to opening the pool...manual leaf cleanup, adding DE, and brushing and vacuuming. I did a few weeks ago clean and lubricate all my pump and filter equipment so that's ready to go. I didn't want to remove the safety cover and expose the water to light until I was ready to SLAM it. Now however, since I see no CYA, it looks like I need to start the pump, retest, and if my CYA still low, add CYA before SLAMing. Since, if I recall from pool school, it takes a while for the CYA to rise, do I have to wait a few days to SLAM it? If so, that means I have to leave the pool untreated until the following weekend to make time to SLAM it. Also, if I need to add borax 20 mule which will affect pH, will the Pool Calculator take all of this into account when recommending amounts of product. Does it matter in what order I add the CYA, baking soda, muriatic acid, borate?
 
Once you have started the pump let it run about an hour and then pull your sample. If the CYA test reads low, let the sample water come to room temperature and run the test again. If it still reads low then you may need more CYA. If you have 20-30ppm of CYA you are good to slam. After the slam is complete you can raise the CYA to 70ppm for your SWG.

Post your test results here before starting the slam and we will tell you if anything else needs adjusting first.
 
Borax is an optional item. After you have completed the slam you can decide if you want to add it to your pool.

You want your pH between 7.0 and 7.5 when you start the slam. 6.8 is the lowest reading on the test, so the actual pH may be lower. After the pump has run an hour run all the tests again and post the results. Your results will tell us what you need to do first.

When you use the poolmath calculator fill in all the "now" values with current test results. It does take all the values into account when recommending the volume of chemicals to add. Play around with poolmath by entering different values in the "now" and "target" columns and see how the recommendations change.
 
Thanks zea3. I hope to have enough time this evening to drain some water to skimmer level, prime the filter with DE and get the pump started and retest the water. Hopefully that will allow me to add some CYA tomorrow and maybe some vacuuming in the evening. Then SLAM Saturday AM. Is it the consensus that all pools need to be SLAMed at opening even if my next test still shows no TC/CC? In other words, there may be nasty things in the pool NOW but no CC only because I have not yet added free chlorine yet?
 
I did not SLAM upon opening. My CYA was 40, FC 4.5, CC 0, pH 7.5, TA 90 and sparkly clear water and zero algae.
 
OK, got home and removed the safety cover, cleaned up some leaves, started up the pump and primed it with DE, started up the automatic cleaner and retested the water after thorough mixing...

pH=7.2
Free chlorine =3, what the...?!?
CC=0, YeeHaa!
TA=30
CYA=48, I can start with that
Salt=2310, Makes sense now
Borate=40
Calcium Hardness=100

So a little mixing answered a lot of my own questions. Should be easy to tweak with the Pool Calculator. Water temp is 45 degrees! So no SWG for a while. I think I'll use my bleach for daily chlorination rather than SLAMing unless I see development of CC. I don't understand how I could still have chlorine in the pool though. It's been closed for over seven months! It will be interesting to see where it goes tomorrow. Should disappear I would think. Will probably do an overnight test this weekend.

Hands on experience...it's a beautiful thing.

Thanks all for your help!
 

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I SLAMMED to 20ppm before I closed in September and opened to 4.5ppm. It gets consumed throughout the winter. My sister thinks it's pretty funny that I'm up and running. HA HA!!! The joke is on her because the longer you wait to open, the less chlorine you have and more than not... it comes with a green pool. I've already peaked under their cover and guess who has a green monster? NOT MEEEEEEE! :mrgreen:
 
Thanks Casey! Overnight test in progress. Major overshoot on chlorine. Added the recommended amount of liquid bleach this morning (about one container of 8.25%, no calculation mistakes I'm certain) and tonight FC=14! No problem though, just surprised. CC still zero.

So, after all the debate about whether I should SLAM or not...accidental partial SLAM! :).
 
If it was dark when you took the sample then get the next sample before the sun comes up. If it's not dropped, you are good to go! :cool:
 
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