Question from newbie on drain and refill of spa

[AndrewFH]

We purchased a swim spa in October of last year. Up until the last couple of months, I knew little about spa maintenance and had just been following the dealer/installers instructions, with less than satisfactory results. In the last couple of months, I have been learning more about it (in large part from this website, so thanks for all the info).
The spa is a 15” swim spa which holds 1425 gallons. It is used for relaxation, exercise and my wife has used it for therapy after her knee replacement surgery. Since it was installed we have done several partial drain/refills. In the near future, I plan to do a complete drain and refill, but had a couple of questions I thought you may be able to help me with.
I have seen several suggestions/recommendations of things to use when I drain/refill the spa, but am not sure of some of them.
Specifically:
One suggestion is to use this product, or something similar (http://naturalchemistry.com/Pool_amp_Sp ... Purge.html) to clear the lines of the spa of any organic contaminants.
Another suggestion is to use a filter on the hose when filling the spa, such as this: (http://www.spadepot.com/shop/Pre-Fresh- ... 4C632.aspx) I live in the Atlanta area (not well water) and our water is pretty clean, so I am not sure if this is of any real benefit.

And lastly, the dealer recommends using this product: http://www.spaguard.com/Our_Products/Ba ... y%E2%84%A2
As I understand it, this is a phosphate buffer (the label says it is “as KH2 PO4/K2HPO4”) to help balance the pH and also removes dissolve metals in your water.

Which, if any of these things are necessary, recommended, or just not worth the extra money?
Any help is appreciated.

 

[chem geek]

Welcome to TFP!

If you have never used a biofilm and grease removal product such as the Natural Chemistry Spa Purge product you linked to or SeaKlear Spa System Flush or Ahh-Some, then it is worth using since new spas are wet-tested and can form biofilms in the pipes that can be difficult to remove with chlorine. However, such a product only needs to be used once and thereafter proper chlorine levels prevent biofilm formation.

The filter hose product only makes sense if you have metals in your fill water, such as with some well water. Municipal tap water usually is not high in metals.

I would not use the Spa Sentry product as that is a phosphate buffer and will create a precipitated mess if there is calcium in the water -- something that will not only cloud the water but will clog your filter. Instead, you can use 50 ppm Borates for supplemental pH buffering and lower the TA to 50 ppm (see Lower Total Alkalinity).

 

[AndrewFH]

Thanks for the quick response chem geek.

 

[chem geek]

Don't forget to look at the Pool School article Using Chlorine in a Spa except you want the TA to be 50 ppm (not 80 ppm) and the use of 50 ppm Borates is a must.

 

[AndrewFH]

I have some follow up questions.
Here are my latest test results:
FC 2.84
TC 3.00
PH 7.5
TA 106
CH 96
CYA 106

I think (based on the study I've done here) that my TA and CYA are high and CH is low. I have read the chlorine article you mention chem geek and am in the process of converting to that method and once I do a complete drain and refill will use that method on the refill.
The reason the CYA is high (at least my assumption) is due to the use of dichlor as the exclusive method of sanitization (one of the recommendations from the dealer that I have learned was not the best advice).
I've plugged those figures into the Pool Calculator and it gives me a CSI of -.35, which as I understand it is not too bad since this is a fiberglass pool (the spa is at 94% as we exercise in it and it is more comfortable there).

I plan to add borates to the water, but want to make sure I've got the other readings in line before doing so.

The spa is under our second story deck and is covered when not in use, so gets very little sunlight. So as most recommend here, the CYA can be much lower. I can do a partial drain to lower the CYA some more, but I am wondering if it is worth it to do so at this time. I plan to do a complete drain/refill in about 60 days. What (if any) are the downsides to just leaving the CYA as is until then? I have some understanding of the relationship between CYA and chlorine demand, but as long as I can live with the chlorine demand, any other problems created by the high CYA?
If I do leave the CYA as is for now, should I use a FC target of 12 as indicated on the Chlorine/CYA chart? Or does that apply more to full size pools? I keep my FC around 2-3 and have no issues (that I know of) with the water quality. It is clear, looks, smells and feels fine.

Once I know what to do about the CYA, and adjust if necessary my plan is to:
Add calcium to get it to 150ppm
Add borates to 50ppm
Adjust TA to 100
Adjust pH to 7.6

Once I get to the above figures the Pool Calculator shows a CSI of -.07.

Any problems/suggestions in regard to this plan?

P.S. One other point that is worth mentioning. This spa has an ozonator. As I understand it this is supposed to reduce Chlorine use, but may actually increase it if the bather load is low.

Thanks for the help.

 

[chem geek]

The spa is under our second story deck and is covered when not in use, so gets very little sunlight. So as most recommend here, the CYA can be much lower. I can do a partial drain to lower the CYA some more, but I am wondering if it is worth it to do so at this time. I plan to do a complete drain/refill in about 60 days. What (if any) are the downsides to just leaving the CYA as is until then? I have some understanding of the relationship between CYA and chlorine demand, but as long as I can live with the chlorine demand, any other problems created by the high CYA?
If I do leave the CYA as is for now, should I use a FC target of 12 as indicated on the Chlorine/CYA chart? Or does that apply more to full size pools? I keep my FC around 2-3 and have no issues (that I know of) with the water quality. It is clear, looks, smells and feels fine.
:
P.S. One other point that is worth mentioning. This spa has an ozonator. As I understand it this is supposed to reduce Chlorine use, but may actually increase it if the bather load is low.

Don't worry about the CSI for the fiberglass. Having the CH in the 120-150 ppm region that helps prevent foaming should be fine for the fiberglass to prevent cobalt spotting as well.

You can live with the spa with its higher CYA right now. It would be a problem if you used the spa every day since the chlorine might not be able to keep up with your bather load in that situation, but if that's the case you may see a higher CC or have more smell (not chlorine bleach smell, but a worse smell). If you don't use the spa heavily, then the extra time should let chlorine do it's job. You aren't in the 200+ ppm CYA region where I've seen spas have problems with bacterial growth that causes hot tub itch/rash/lung if the FC isn't kept much higher. I would target 2-3 ppm FC for the start of your soak and just dose appropriately after your soak -- that is, do as you normally would if the CYA were in a better range -- it's not so far out of whack as to cause problems since I presume the spa is covered so is unlikely to get algae.

Your understanding about the ozonator is correct. Your dosing after your soak will be less then without an ozonator, but your required dosing in between soaks will be higher.