Can't keep chlorine in spa water?

[spanoob9]

Every night I've been adding dichlor up to 5 ppm fc and in the morning its back down to .5 - 1 ppm. This is ever since I refilled it after neglecting the spa for about 2 months. Also at some point in that 2 month period the circ pump died.. So new pump, drained the water, refilled. Now something's using up all the chlorine.

The waters perfectly clear, no smell/cloudyness/scaling anything like that. I did check the filters which I cleaned 3 days ago during the refill, and they had yellowish brown stains all over, not sure if that is bacteria growth or from all the chlorine I've been adding?

Also I was recommended to test the phosphate level and its high at 500 ppm (fill water is 500ppm).

Other info I do have an ozonator, its 500 gallons, 4 years old

So any ideas?

 

[Donldson]

How long have you been adding this dichlor? You have been raising your CYA by about 4 ppm every night so you are looking at probably having an overstabilization problem. Do you have a CYA test?

On the phosphate side, they are measured in parts per billion, so your level is 500 ppb, or 0.5 ppm. If you are keeping proper FC levels they won't really matter. Just also wondering, is this an indoor or outdoor spa, and are you using dichlor for a specific reason?

 

[spanoob9]

How long have you been adding this dichlor? You have been raising your CYA by about 4 ppm every night so you are looking at probably having an overstabilization problem. Do you have a CYA test?

On the phosphate side, they are measured in parts per billion, so your level is 500 ppb, or 0.5 ppm. If you are keeping proper FC levels they won't really matter. Just also wondering, is this an indoor or outdoor spa, and are you using dichlor for a specific reason?

My test strips do test stabilizer, they've been showing between 30-50 ppm. I haven't really noticed it changing much

Its outdoor. I'm using dichlor because everyone I've talked to that owns a spa says its the easiest sanitation method

 

[Donldson]

For every 1 ppm of chlorine you add using dichlor you also add 0.9 ppm of CYA. Eventually your water gets overstabilized and you end up with problems. The easiest way to add chlorine is liquid as it doesn't add CYA or calcium. Test strips are so inaccurate I don't believe a word they say.


I might have missed in your first post, did you just refill 3 days ago? If so have you added anything else besides dichlor in that time?

 

[spanoob9]

For every 1 ppm of chlorine you add using dichlor you also add 0.9 ppm of CYA. Eventually your water gets overstabilized and you end up with problems. The easiest way to add chlorine is liquid as it doesn't add CYA or calcium. Test strips are so inaccurate I don't believe a word they say.


I might have missed in your first post, did you just refill 3 days ago? If so have you added anything else besides dichlor in that time?

Yes i filled it 3 days ago. I did add a I think an oz or so of alkalinity increase to balance the water. I've been adding dichlor granulers about everyday and today i added this other stuff I found its called spa boss energize "oxidizing shock treatment" it says works with chlorine. Not sure if it helped at all

 

[Donldson]

Well then I am sure your test strips are inaccurate, your CYA should only be about 20. You haven't overstabilized your spa yet then, but you will if you continue to use dichlor. If you cover your spa during the day then your best bet is to stop using it after this weekend and switch to plain unscented bleach. It will chlorinate exactly the same but without any side effects that dichlor will have. You can use the pool calculator to figure out how much to add, it will not be very much. If you don't cover your spa then keep using the dichlor another week and then switch to bleach. Bleach will be just as easy to use as dichlor but will not add CYA to your spa.

The spa boss stuff probably helped oxidize something if there is something that needs oxidized, but is really designed for bromine tubs. Do you have any test kit other than strips? Even one of the ones that uses drops to test chlorine and pH would be a help here.

 

[chem geek]

Same thread as at poolspaforum.com here. Though spa is not new, it was unused for 2 months and likely did not have the pipes blown/dried out so it's possible that biofilms formed and are still active creating high chlorine demand. I suggest using SeaKlear Spa System Flush or Ahh-Some, then possibly superchlorinate to decontaminate as described here and then dump the water (one can dechlorinate before dumping if one dumps into an area with plants).

Also note that there is an ozonator installed. If it is on for too long or too powerful, then it will increase chlorine demand in between soaks, though I've never seen it be more than a 70% demand (more typical is 50% compared to 25% with no ozonator). If the ozonator were functional, then the required chlorine demand from bather load would be lower (roughly cut in half, though again depends on the on-time and strength of the ozonator).

 

[spanoob9]

Thanks for the input.

Last night I put in a whole mess of dichlor and also some phosfree and my fc level is still high which seems to be a good sign.

I also picked up some spa purge if I still have high chlorine demand. I did drain the spa 2 days before I refilled it so not sure of that reduces the possibility of having biofilms in the pipes or not.

 

[chem geek]

So either the chlorine killed off what was growing or the phosphate remover starved it or both. I'd still do a spa flush and possibly decontamination on your next water change just to be safe.

Just note that when you add Dichlor you are increasing CYA which makes chlorine less effective. For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm. That's why we say that once you have an established level of CYA, you should use bleach instead of Dichlor, but when doing that you need the TA to be low (50 ppm) and to use 50 ppm Borates for additional pH buffering.

 

[spanoob9]

So either the chlorine killed off what was growing or the phosphate remover starved it or both. I'd still do a spa flush and possibly decontamination on your next water change just to be safe.

Just note that when you add Dichlor you are increasing CYA which makes chlorine less effective. For every 10 ppm FC added by Dichlor, it also increases CYA by 9 ppm. That's why we say that once you have an established level of CYA, you should use bleach instead of Dichlor, but when doing that you need the TA to be low (50 ppm) and to use 50 ppm Borates for additional pH buffering.

Hmm strange because my test strips show stabilizer at the same level nearly everytime, the scale is 0-300 ppm and fc is 0-10 so that might be why

 

[chem geek]

Test strips are useless, especially for CYA testing. You should get your own quality test kit, either the TFTestkits TF-100 or the Taylor K-2006.