robquick

If I've got Biofilm is a water change the only way to resolve ? What are the signs of a need to change water other than smell or colour? Is there any signs from the water tests I complete daily ? Thanks again.

Thanks Chem. The tub is 1500 litres with Ozone and the temp was set at 37 degrees throughout. I think I understand your explanation however, I do have one question. If generally you need 3x CC level to reduce CC why did my 10x reduce to 5ppm FC within hours ? One final question, the water is crystal clear with no smell however, since my problem last weekend my daily FC demand has increased from 60% to around 85%. Is this a fundermental sign of a water change, if not, what are the signs ? Thanks.

Hi, On Saturday night six of us used my tub for about 1 hour, once we had got out i put 6x40ml of 15% bleach (40ml per person hour normally gives me a 2-3ppm reading 24 hours later). 24 hours later I checked the water for FC and I had a high reading on my Photometer suggesting the FC was over 6ppm. Due to the high reading i didnt add any additional bleach, 24 hours later the water was very cloudy and clearly wasnt right. I tested the water and the FC was zero and the CC was around 4ppm (!!). Due to the very high CC I added enough Chlorine to raise the FC to 40ppm and put the filters on, within hours the water started to clear and the FC was back down to around 4-5ppm. Three questions - When I put the FC up to 40ppm I assumed it would take days to drop back down however, within 12 hours it was sitting at about 4-5ppm. Is that what you would expect and is that due to the water needing the Chlorine to clean the cloudy water (which it did) ? I'm getting suspect readings with the DPD1 tablets I use in my Photometer, if I put a DPD1 tablet in two separate vials with the same water sample I can get two VISIBLY different colurs of pink (hence the reason I didn't put any additional bleach in on the second night) - can this be anything other than faulty tablets?? If you get very high levels of CC how do you calculate how much FC is needed to resolve the issue. I read somewhere that roughly you need 10x the CC level which is what I used and it worked albeit I read somewhere this calculation is rubbish !!?? Regards.

Hi both, Prior to my holiday I switched off the tub and after it had cooled I raised FC to 15ppm. Having returned 11 days later my FC was reading 'Hi' on my photometer indicating the FC was greater than 6ppm which I was pleased with. A target of 10-12ppm would have possibly been better for next time however, either way the water is safe which was my main objective. With respect to my CC I took a water sample when I returned, once the FC has dropped to a lower level I will be able to get and accurate CC reading which should then indicate the impact that the Ozone has been having on the CC levels (water sample was with Ozone off for 11 days). I will update you over the next few days as requested. Cheers.

Both, I'm going away on holiday for 10 days as of next Tuesday, my intention is to turn the tub off and then dose with a high level of Chlorine and leave until I return. I'm guessing this would be an ideal time to see what impact having the Ozone switched off has on CC? If its not the Ozone impacting my CC levels what would you try next ? On a separate note what level would you dose the FC to prior to my 10 day holiday to ensure I maintain an acceptable FC level for the duration of my holiday ? I will update you on the Ozone/CC levels when I return. Thank again.

If I was to disable the Ozone how long would it take before I could take an accurate CC reading ? Thanks.

Waterbear, Thanks for the reply. Are you saying that this is a short fall of DPD testing, some Ozone systems or both ? Is there a testing method that doesn't suffer the same problems when measuring CC ? What's the problem with how some Ozone systems are installed ? If I was to disable the Ozone and not use MPS for a week or so are you suggesting my CC would measure considerably lower ? My water is crystal clear and smell free which suggests your theory is correct (ie something is generating inaccurate CC readings). Apologies for the mass of questions however, I'm generally interested in understanding what's happening in my tub !! Once again, thanks for your reply.

Yes, I have Ozone. I don't shock with MPS as my belief was that there was no need with the Dichlor/bleach method provided you always maintained good FC levels however, I did use MPS earlier today to see if it made a difference, I haven't re-tested yet. I'm testing with a Lovibond professional Photometer. Thanks.

Sorry ....... and 50ppm Borates.

Hi, After a recent water change I changed to the Dichlor/bleach method and have since had real success with exceptionally clean looking water however, I'm really struggling to obtain an acceptable CC level. I had the same issue before when I converted to the Dichlor/bleach method half way through a water cycle, I put this down to the high CYA (90 ppm) at the time I converted. I can't understand what I'm doing wrong as the fresh water was 0.20ppm CC and since then its slowly risen, after about four weeks it now sits at 1.75ppm CC. I'm *** with checking the levels and I never let the water go under 1ppm FC, the tub is used for about 3 bather hours per week. The levels are as follows. FC - 3ppm CC - 1.75ppm TA - 50ppm CYA - 35ppm PH - 7.54ppm CH - 110ppm Any help would be greatly appreciated. Thanks.

Hi, Tesco's sell 2 litres of Value bleach (less than 5% in strength) for 0.29p. I understand that I would use fairly large volumes due to the strength however, due to the cost it would still work out very cheap and would be convenient as I shop weekly at Tesco. A few question.......... Would this bleach be ok to use in my tub ? I believe this bleach could be high in levels of 'Lye', what is 'Lye' and why is it a problem ? Does anyone know how I could find out the levels of Lye in Value bleach ? Has anyone got any experience of using this bleach for their tub ? Thanks.

I've recently completed a water change, the waters not bad just not as clear as it was on day one, and certainly not as clear as the shops water. I would describe their water as looking 'silky'. Does clarifier have any negative impact on the water like anti foam can ? I thought I read some where that it blocks the filter up? Thanks.

Hi, I use the Dichlor/bleach method of water maintenance which works really well however, when I visited my hot tub store today I noticed how 'blue' their water is compared to mine. Having spoken to the chap in the store the only noticeable difference in terms of water maintenance was that they use clarifier. Would you guys recommend clarifier? Is there a negative impact in using it (IE does it screw up the balance of the water in any way)? Thanks.

With the power being off is there a problem with the water not being filtered in any way ?

Ok, think I will leave it then. One last question, I'm currently at the stage of adding Dichlor to raise my CYA. Over the last four days I've raise my FC to the following levels. Initial water fill 0.28-10 FC Day 3 (3-6 FC) Day 4 (4-6 FC) Dat 5 (4-6 FC) Having checked my CYA on day 6 I expected my CYA to be around 16ppm however, it was only 6ppm is that unusual ? Thanks.

Would you leave the ph at 7.8 or reduce it down to 7.6 ? Thanks.

All chemicals are now added including Boric acid, I've tested the water again the TA is 47ppm however, my PH is 7.8, is that ok or too high ? If its too high, with 50ppm Borate I've calculated I need 20g of acid to get the PH to 7.6 (pool calculator). I assumed it would need more acid than that due to the Boric acid, can you confirm my calculation ? I guess I will then need to add some Baking soda to bring TA back in line ? Thanks.

What impact does Boric acid have on TA when added to the tub ? Thanks.

ChemGeek, I have a few questions I would appreciate your help with. Is TA 'up' always the same chemical ? Am I right in assuming that TA increaser has little impact on PH ? When using the Dichlor/Bleach method the recommended TA is 50ppm, I know it's safe to have the TA at this level however, what's the theory behind it as all Spa manufactures recommend safe levels being 100-120ppm ? Apologies, I have asked the question before but I can't remember the answer ! Thanks.

Just a thought but the 'AKA' for chemicals that you've listed above is really helpful for people like myself that are new to hot tubs. Is there any chance a comprehensive list could be put together and added as a 'sticky' ? I appreciate I'm volunteering someone else to do the work but it would be really helpful !

No problem. I appreciate its a daft thing to say however, I wanted to check as adding 429g of any chemical into the tub felt a bit unusual compared to normal quantities of chemicals I have to add ! I've managed to get TA to 47ppm and PH to 7.9ppm.......the next step is to add the Boric acid !! Thanks again.

My tub is 1480 liters which equates to 330 gallons, is there a UK/USA conversion issue for gallons ? In the UK 1 gallon is 4.546 liters therefore 1480/330 is correct, have I got something wrong for the Boric acid requirement ? Thanks.

Thanks, really helpful explanation. Looking through the cupboard I've also a tub of PH increaser which contains Soda ash. How does this fit into the equation ?

Does anyone have a 'link' for ordering Borate test strips in the UK ?

Hi, I'm getting a little confused with the process of reducing TA. On this site it talks about reducing PH with 'acid' to 7.0ppm and then aerating to increase PH. What exactly is 'acid' ? I use Sodium Carbonate and Sodium Bisulphate to increase/decrease PH. Do these two chemicals have any significant impact on TA or is 'acid' a completely different chemical ? Can I buy 'acid' in the UK ? Thanks.