cocoabailey Posted March 7, 2009 Report Share Posted March 7, 2009 Hope everyone is having a great weekend. I was soaking in the tub last night and was thinking about how good the borates make the water feel. The pool calculator uses borax to raise the water to the desired level (around 50 ppm, which equates to around 600 g of borax, then you have to add acid) to bring the PH back down. This is a one time shot per fill. With the stuff you get at any spa depot, they are generally PH balanced so you don't have to worry about PH. However, they generally have to be added weekly after an initial dose (150g/1000l, then 40g/1000l after that per week). Does anyone know why this is? Couldn't you just add them all at once like the borax and not worry about it? The end result is about the same amount of actual product being added over time (approx 600g using my own 1500l tub as an example). Perhaps this is how manufacturers control Ph spike, by adding it over time. Can anyone offer a more educated guess than my own? It was interesting to note when I spoke with a local spa dealer today, they didn't even think borates help provide a Ph buffer! Anyway any insight would be much appreciated as always. Thanks, T Quote Link to comment Share on other sites More sharing options...
chem geek Posted March 7, 2009 Report Share Posted March 7, 2009 I find no good reason for their recommendation to have one larger dose followed by smaller doses weekly. Having an initial dose should be all that is needed since the borates do not dissipate. In a pool, there is splash-out and backwashing (depending on filter type) so some weekly addition to make up for such dilution makes sense, but that doesn't happen to a great extent in a spa. Remember that evaporation and refill doesn't change the concentration of chemicals in the water (except to add to the spa whatever is in the fill water). Quote Link to comment Share on other sites More sharing options...
cocoabailey Posted March 7, 2009 Author Report Share Posted March 7, 2009 I find no good reason for their recommendation to have one larger dose followed by smaller doses weekly. Having an initial dose should be all that is needed since the borates do not dissipate. In a pool, there is splash-out and backwashing (depending on filter type) so some weekly addition to make up for such dilution makes sense, but that doesn't happen to a great extent in a spa. Remember that evaporation and refill doesn't change the concentration of chemicals in the water (except to add to the spa whatever is in the fill water). Hi Richard, Thanks for the reply. I couldn't agree more! I think the only difference is you end spending more money on chemicals, raising the TDS even higher, and making it necessary to switch water more ofter....hence spending more money on start up chemicals, it is a vicious cycle! I think I'll try the pool calculator recommendation of borates to add for my tub size and see how it works out with my ph stable brand. I ordered my TF100 kit today. It should be here soon! I am excited! (for those reading this thinking get a life...I truly find this subject fascinating!) This is much more interesting than just using a floater and bromine! One last quick question, when adding bleach, does it matter if it is before or after a soak? Thanks, and have a great weekend! T Quote Link to comment Share on other sites More sharing options...
chem geek Posted March 8, 2009 Report Share Posted March 8, 2009 One last quick question, when adding bleach, does it matter if it is before or after a soak? This depends on your goals. If you are concerned with person-to-person transmission of pathogens, then you would make sure the FC is high enough before the soak to handle the bather load so that you still measure some residual FC after the soak. However, the downside is that you will likely notice the bleach and probably smell some chlorine or monochloramine during the soak. The other alternative is to add the bleach after the soak making sure it's enough so that the next time you soak you measure a small residual FC just before the soak -- around 1 ppm FC (most people don't notice that level of chlorine). The downside is that bacteria won't get killed during most of your soak since the FC will have gone to zero combining with the ammonia from your sweat to form monochloramine. Your addition of bleach right after your soak is likely to kill anything you introduced during your soak since it takes 15-60 minutes for bacteria to double in population and also takes a while for them to form thick enough biofilms that chlorine can't attack easily. So adding bleach after the soak is probably pretty reasonable depending on whom you invite over to soak with you. Richard Quote Link to comment Share on other sites More sharing options...
cocoabailey Posted March 8, 2009 Author Report Share Posted March 8, 2009 One last quick question, when adding bleach, does it matter if it is before or after a soak? This depends on your goals. If you are concerned with person-to-person transmission of pathogens, then you would make sure the FC is high enough before the soak to handle the bather load so that you still measure some residual FC after the soak. However, the downside is that you will likely notice the bleach and probably smell some chlorine or monochloramine during the soak. The other alternative is to add the bleach after the soak making sure it's enough so that the next time you soak you measure a small residual FC just before the soak -- around 1 ppm FC (most people don't notice that level of chlorine). The downside is that bacteria won't get killed during most of your soak since the FC will have gone to zero combining with the ammonia from your sweat to form monochloramine. You addition of bleach right after your soak is likely to kill anything you introduced during your soak since it takes 15-60 minutes for bacteria to double in population and also takes a while for them to form thick enough biofilms that chlorine can't attack easily. So adding bleach after the soak is probably pretty reasonable depending on whom you invite over to soak with you. Richard Great, that is the way I have been thinking about it. Big loads (ie party) you'll want to up the does first, but if it is just me or my spouse and I, the shock can wait till after the soak. Thanks again for the info. It is truly amazing what you can learn on line, with the investment of some time! T Quote Link to comment Share on other sites More sharing options...
Nitro Posted March 8, 2009 Report Share Posted March 8, 2009 Cocoa, Normally if it's just me and the misses, I just make sure there's 1-3 ppm FC, and add bleach after the soak. If I have guests, I'll have at ~6 ppm FC and add bleach every 30-60min depending on usage. When I have hot tub party's I'll check the FC with test strips every 30-60mins to get an idea of how much is being used. Think of it as "Trial & Error". Also, if you have a high bather load day, consider adding MPS BEFORE (and during) the soak. It will help oxidize waste freeing your Chlorine to kill bugs. Just keep an eye on TA/pH when using MPS, because it will lower it. If you have already ready seen it, My Post under Sanitation has some guidelines and examples. Quote Link to comment Share on other sites More sharing options...
Jim F Posted March 16, 2009 Report Share Posted March 16, 2009 Richard and Nitro, I keep reading about MPS and its value. This thread is the last I have seen you mention MPS I believe that using MPS will alter effective DPS chlorine testing afterwards, for how long I dont know What do you do to correct this, especially since you, Nitro, are checking chlorine levels as you soak? Thanks for your continued help Quote Link to comment Share on other sites More sharing options...
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