SLAMing a spa

[3dogowner]

a few SLAM questions -
1) when SLAMing, should filter cycles be turned off and circulation pump only be left on 24x7? I have ability to program it this way.... my understanding is that FC will drop with aeration and bather load and organics, so I'm wondering if filter cycle counts as aeration time.......
2) does higher water temp (98F) affect FC loss more? or should OCLT rules hold for a spa as much as a pool? this is a covered outdoor spa with NO sun exposure during this SLAM being checked only late at night.
3) If a day or two are missed in the SLAM process, am I back to square one? very difficult with work schedule to check every day even once a day (OOT). Have others had success with just slogging away at it when they can?
4) If the spa is used during the SLAM process, am I back to square one? water has always been clear so hard to resist using it...but FC won't hold and CC hovers 0.5-1
5) can spa pillows hold organics? I've pulled them and dumped them in a bucket of bleachy water to sit overnight
6) has anyone had to replace the weir just to remove the last of the organics? mine is under the waterline, so shouldn't that be enough exposure to eventually get it clean?
7) is the SLAM after a Baqua to chlorine conversion more prolonged and painful than if I had just always had chlorine or bromine in the spa?

 

[tim5055]

A couple of your questions point to the fact that you are not able to follow the guidelines for the full SLAM Process.

As we are only talking about 390 gallons or so why not just a full drain/refill? A stand alone spa not interconnected with a pool really should have a drain/refill a few times a year anyway.

Have you read " How do I use Chlorine in my Spa"?

 

[chem geek]

Spas are more complicated due to the lower water volume where bather load dominates and where the use of additional devices such as ozone or UV can have a significant impact on chlorine demand. You generally should not need to SLAM the spa if you are properly maintaining it.

In a hot (104ºF) spa with no ozonator or UV, the rough rule-of-thumb is that every person-hour of soaking requires 3-1/2 fluid ounces of 8.25% bleach (or 3-1/2 teaspoons of Dichlor or 7 teaspoons of 43% MPS non-chlorine shock if using Nature²). For a covered spa, you don't do an OCLT but rather look at the 24-hour percentage chlorine loss in between soaks at least one or more days after the last soak. A normal drop is 25% or less. If you have an ozonator (you don't, but for others to know), then the chlorine drop can be 50% or more since ozone reacts with chlorine (a UV system can also break down chlorine). The benefit of the ozonator is if one soaks every day or two in which case the chlorine demand from bather load is cut roughly in half.

If you converted from Baqua by doing a complete drain/refill, you may have some leftover Baqua in the pipes (you would need to replace your cartridges in the filter) then you may find some initial chlorine demand but still shouldn't need to shock unless the water wasn't clear.

 

[3dogowner]

Thanks chem geek -

I did a full drain/scrub/rinse/refill after superchlorinating for 24 hrs/and filter change 14 days ago.
I've read everything multiple times over.

The CYA is not measurable today, although it was added in theory to ~35 more than 7 days ago, the pH is 7.5-7.8 (started at 7.2 4 days ago), the TA is 40-50 and the CH 140 and Borate level of ~50. No ozonator, no UV system, no nature
FC last night was 17 with CC of 0.5, this morning with only circulating filters on overnight and the pillows pulled out of the spa overnight, FC 13.5, CC 0.5. This amounts to about a 20% drop but in a 12 hr time interval, not 24 hr.

BTW, correct me if I'm wrong, but with a CYA <30, an FC of 17 should be definitely more than adequate for a shock level. Every 2-3 days, I have used the Pool Math calculator and bumped the FC to at least 10, if not higher.

I will keep cleaning, wiping, and changing the filter frequently this first post-Baqua/now-chlorine month and aim for a measurable CYA of around 30-35. I'm hoping that by having it in a sock in the weir that it didn't get all got up in the filter and thus pulled out when I pulled this filter 5 days ago. I did not just dump it into the filter area. Does CYA only stabilize the chlorine from sunlight?

I have to change out the diverter valve, so maybe that will help. And I figured I may as well change out the weir gate as it's 14 years old and may be harboring stuff. The pillows are sitting in a bucket of bleach water for 24 hrs, so maybe that will help as well - only 2 of the 3 are still original to the spa and all 3 look great and clean.

 

[chem geek]

You shouldn't need to shock but instead should add the amount of chlorine after a soak to handle your bather load. With no ozonator, every person-hour of soaking in a hot (104ºF) spa requires roughly 3-1/2 fluid ounces of 8.25% bleach or 3-1/2 teaspoons of Dichlor.

So that's not a good sign that you are not measuring CYA in spite of adding it. Perhaps the CYA is in the filter still dissolving though in a hot spa it dissolves more quickly than in a pool. If there is no CYA in the water, then the active chlorine level will be too high (so no, it's not just to protect chlorine from sunlight but also significantly moderates chlorine's strength). The chlorine loss rate will be higher as a result, some of the chlorine outgassing. I'd look at the 24-hour loss once you get 30-40 ppm CYA actually in the spa. I assume you are using a proper test kit such as the TFTestkits TF-100 or the Taylor K-2006. Otherwise, with test strips or other methods the CYA test is probably not valid/accurate.

If you add the proper amount of chlorine after each soak, then you should not ever need to shock/SLAM.

 

[3dogowner]

I will try to bump the CYA to 30-40 and see what happens. Maybe it's a combination of higher loss rate due to too low a CYA level and a smidge of hidden organics.....I'll keep at it and get back to you.
Huge thanks.

 

[3dogowner]

Went on-line to look into what it takes to measure the CYA at 20+ppm. Both Taylor and TFT will sell the 9193 CYA view tube that is calibrated from 20-100 ppm, both for under 3$. Several pool supply websites will also sell it, but for much more. TFT has a reasonable shipping price. So the only difference in the 30-100 ppm test and the 20-100 ppm appears to be the tube (length and diameter). The reagent mix standard is a 1:1 ratio. I just read elsewhere on TFP that the 20-100 ppm tube requires 30 ml to reach the 20 ppm line. So 15 ml of water, 15 ml of reagent. There you have it. Cheaper than buying an entire test kit. Why they don't include it in the first place.........except clearly if you favor the lower CYA concentration, you will use a little more than double the amount of reagent.

 

[chem geek]

The TFTestkits TF-100 DOES include the tube for measuring 20 ppm. It's the Taylor K-2006 that doesn't and is one reason why we recommend the TF-100. You can see the Pool School article Test Kits Compared. You get more CYA tests in the TF-100 that has a more logical balance of reagents (they are still Taylor reagents -- just in quantities that make more sense).

Even without the 20 ppm tube, you can tell if you have some CYA if the water even up to 30 ppm is cloudy in the tube even if it doesn't completely obscure the black dot.

 

[3dogowner]

A quick follow-up....
Water clear, no foaming, no ring. Temp at 98F. CYA now measurable at ~30 ppm, TA at 40-50, CH at 140.
FC dropped after 4 days of non-use from 10 ppm on Sunday night to 1.2 ppm Thursday morning (in theory a >25% drop per 24 hr). CC at 0.5.
Used the spa, then bumped it to 8.5 ppm last night, down to 6 ppm this morning (def a >25% drop just overnight).

Changed out the diverter valve last night, at least a 1 mm coating of Baqua gunk on the valve rotater axle portion. Pillows have been out now a week.
I suspect the chlorine is eating away at Baqua slime in the pipes somewhere. The new weir gate is here, so I'll replace that next.

I'm getting a feeling now that I will need to replace the chlorine by adding back 4 oz per person hr (a little more than the 3.5 oz that you had mentioned) PLUS another 1 oz (a generous ounce) to cover the anticipated average overnight loss (25-30%).
To deal with hidden Baqua gunk, I think I'm just going to be patient and wait for when I next do a flush and fill (likely Jan, the 3 month mark). At that time I will flush the pipes 36-48 hrs. I would have thought the 24 hr flush I had done during the conversion earlier this month would have been enough, but obviously not. That's what happens after letting a pool store maintain it with Baqua for 14 years. If I can fix this in just under 4 months, I'll be happy. Perhaps the 24 hr loss will drop to <25% before then, if so, great.

Any thoughts?

 

[chem geek]

I think you're on the right track. If there's leftover Baqua, then that will get oxidized by the chlorine and you may see your chlorine demand drop a little as it gets used up, but you're close to "normal" for a hot spa with no ozonator. The key is to maintain a chlorine level so it doesn't get to zero. So just figure the daily 25% or so plus what you need to handle the bather load. Sounds like you've mostly got this dialed in.