macgd016

I have a 13,000 gallon pool and want to know what my Chlorine Demand is or should be. pH is 7.4 and CYA is 200, high I know but thats where it is and pool temp is 82F. The pool is crystal clear and has a very light load, just two people having a quick dip each day and the phosphate level is negligible. I have an automatic chlorine pump and have assumed that my chlorine demand would be around 1ppm per day so have added 23oz of 6.8% chlorine each day. This has been fine for the past 5 weeks but recently, as the temp as gone above 80F, I find that FC & TC are dropping daily so a)I can't see why this should be and other than by trial and error can't see how much chlorine I should be adding.

I am confused, I have 3 different makes of test strips and they are all showing FC & TC of 1ppm give or take but my OTO tester shows 4ppm, can this be right?

24 feet by 12 feet? That would be a lot more than 1,300 gallons. 12 feet by 24 feet by 4 feet deep would be 8,640 gallons. Bromine really isn't that hard. Just add 8 ounces of sodium bromide, then just use liquid chlorine, and treat your pool as if it was chlorine. 12 feet by 24 feet by 4.5 feet deep would be 1300 cubic feet. Is that what you mean? My mistake, I work in metric and the pool is 3.6m X 7.5m 1.8m giving 48,000 litres or roughly 13,000 US gallons.

Thank you both for your replies. For the present I am stuck with a high CYA, this is not a 'cost' issue but a legal and social one. Up until last winter Southern Spain had had no appreciable rain for 4 years and reservoirs were at critically low levels. There was a slight recovery last winter but it is still illegal to fill pools and water supplies to houses are regularly (daily) cut for several hours during the summer. Although our pool is indeed small it still contains about the volume of water that would be used by a small family in 4 months so it is for this reason that I a) do not wish, and am not permitted, to refill it. It is my intention to switch to an automated liquid chlorine system this winter which will stop any further increase in CYA and will enable it to be reduced over time through natural dilution. So for the meantime, as I tried to explain in my initial post, I am stuck with a high CYA level, I have no desire to switch to Bromine as I have no experience of it and more importantly there is little or no experience of it locally so I need to manage my pool as it is. We have been managing to successfully keep the pool under control but some unexpectedly high usage last week caught us out and we now need to rectify the situation. From the excellent information I have gleened on this forum I now have an understanding of the relationship between CYA and FC and using the Pool Calculator can see that in order to shock the pool I need to raise the FC to 75ppm. I also believe that as 75ppm FC with 400ppm CYA is equivalent to 16ppm FC with 50ppm CYA it should be perfectly safe to swim in but I just wanted to check and to see whether there was any other advise out there. For info the pool is 24x12, 1,300 US gals and all other readings are well in spec.

Anybody!

My pool is in southern Spain and I found earlier in the year that although the CYA was very high, 400ppm. I recognize that I should drain the pool and start again but there is a major water shortage in Spain and re-filling pools is not permitted. The house is let out over the summer and we have been managing to maintain the pool very successfully since June by keeping the FC at about 10ppm and using Algaecide, fortunately for us we are almost phosphate and nitrate free one benefit of living in the mountains and using what is essentially mountain spring water. Unfortunately we have just had one family stay at the house who, despite being advised to the contrary, have used lashings of suncream and splashed so much that the skimmers were sucking air after only 2 days!! The end result is that we have algae. We first found this yesterday and have hit it twice with double the normal dose of GR90, which is a 90% available Trichlor granule, and having the pump on 24h, adding more algaecide and crystal clear to help with filtration. My calculations suggest that the shock treatment will raise the FC by 16ppm and although the FC is falling back to 3ppm it is having an effect, the water is clearing and you can see the bottom and there is quite a bit of dead algae on the bottom which we have hoovered out, but the water is still green. As we have guests staying at the house I really want to get the water good and clean as quickly as possible whilst still letting them swim. Using the pool calculator I have calculated that with a CYA level of 400ppm I need raise the FC to 75ppm to shock it and this will need about 1 gal of 10% bleach. From what I have read this is still a perfectly safe level of chlorine to swim in but I just wanted to check before going ahead. Any other suggestions as to how to proceed would also be welcome.

Hey thanks for this, it looks just right for what I would like to do. Richard, have you ever considered using one of these? Apart from the obvious drawback of having to lug chlorine around it looks like the perfect solution.

The instructions on my algaecide tell me that I need to dose the pool initially and then give it a weekly top up. Why is it necessary to give this top up, does the algaecide get 'consumed' . Are there any drawbacks to them, I have heard of green hair for instance.

I have a 50,000 liter pool, the pool calculator shows that an 8oz puck will give me 4.2ppm FC and 3ppm CYA. Assuming for convenience a FC usage of just over 1ppm per day I will need 2 pucks a week which will increase the CYA by 6ppm. To bring the CYA back to a starting point of 50ppm will require 11% or 5500 liters of pool water to be drained and replaced weekly!! If the pool pump has a flow rate of 300l/min this is 18 mins of backwash. Is this right or have I got something badly wrong. Richard Sorry to be a pest but do these calculations look about right, total accuracy is not important just the order of magnitude Mac

Unless I am missing something (which is quite likely) choosing the right model is quite difficult. We know that we need about 1ppm per day FC and how long we want to run our pumps, but the SWG manufactures quote there devices in grams per hours. I have no idea how you convert grams per hour to ppm though!

The Code-91 fault code is low salt. From what I can see there are two main draw backs to the Intex system. They are sized for small pool but their spec says that they can handle up to 50,000 litres or just over. For pool of this size they need to be running for 12 hours a day in the summer which with a small pump is not a major problem but will use 450w per hour. However, the cell only has a life of 3000 hours so you will need to renew it every year. The other issue is that the timer needs reseting if there is a power outage.

Hi, Yes I have tried them but I'm not at all sure they worked at all

I guess there must be a catch but these Intex SWG http://intexsaltwater.com/productinfo.html are cheap and although designed for AGP have a max output of 24gm/h which is not bad and will cope with 50000 litres which is what I have. Does anyone have any experience of these units?

It shouldn't. It WILL affect the chlorine effectiveness, but not the chlorine test readings. Why do you ask? As I mentioned in an earlier post my pool guy let the FC go really high about 3 weeks ago. It was probably still 12-20ppm a week ago and it still hasn't come down to 10ppm. This was at the same time I found my CYA was through the roof, a recent measurement using dilution suggests it may be 750ppm. I was just wondering whether the FC reading might be effected by the CYA. However, there will be very little FC usage as the pool is still quite cold, 22C and nice and clean and not in use which is probably why its not dropping very quickly. PS. Many thanks for all your input to my various posts, quite invaluable to me as I struggle to understand what is and has been going on and what to do about it in the short and long term. Mac

Can a very high CYA reading effect FC and TC readings?

You can't get electronic dosing but as it injects a precise dose per hour and only works when the pump is on so it is easy to work out what does you will get.

Having decided that I need to get away from Trichlor chlorination I have been looking at the alternatives. I have just found this product www.chemilizer.com and wonder whether anyone has any experience or views on it

So unless your house in Spain is mainly on the plain ... (sorry, couldn't resist) Actually its in the mountains but that is another story. Thanks you both for your replys, I am fast coming to the view that I need to install a SWG but I'm concerned that doing so may necessitate running the pool pump for longer than I am doing currently. Try as I might I can't find any information on the length of circulation time needed to achieve a given 1ppm FC, or do SWG's work independently of the circulation. I can see that a SWG may just produce chlorine when its on and this will then be pumped into the pool when the pump is on but I'm not sure if they work this way or not. If the above is a problem I could plumb an Intex Krystal Clear Chlorine generator into my Solar Heating system which has a separate low wattage pump. These systems are designed for above ground pools but are supposed to work with pools up to 20,000 gals. Given that they are inexpensive I suspect that they may not be up to the job though.

Yes, I meant 1 ppm per day chlorine usage and I've edited my post to correct that. You can use The Pool Calculator to see that one 3" puck weighing 8 ounces added to 8000 gallons adds 6.85 ppm FC and 4.2 ppm CYA. Some 3" pucks weigh 7 or 6 ounces. 1" usually weighs 3 ounces and 1/2" usually weighs 1 ounce so you can scale accordingly. Thanks for the pool calculator, it is really useful but gives some worrying results. I have a 50,000 liter pool, the calculator shows that an 8oz puck will give me 4.2ppm FC and 3ppm CYA. Assuming for convenience a FC usage of just over 1ppm per day I will need 2 pucks a week which will increase the CYA by 6ppm. To bring the CYA back to a starting point of 50ppm will require 11% or 5500 liters of pool water to be drained and replaced weekly!! If the pool pump has a flow rate of 300l/min this is 18 mins of backwash. Is this right or have I got something badly wrong.

First figure out how much CYA you are adding every month. For every 10 ppm Free Chlorine (FC) added by Trichlor, it also increases Cyanuric Acid (CYA) by 6 ppm. So if you have even a low 1 ppm FC per month chlorine usage, then this is 1*30*0.6 = 18 ppm CYA per month. Then figure how much you need to dilute based on your CYA level target range. If that is 50 ppm on the low end, then after a month it's 50+18=68 ppm CYA so the amount of water required for dilution is 18/68 = 26% which is a lot. That's why even with backwashing it's hard to keep the CYA level lower unless there is rain overflow as well. If your target CYA is higher, say 100 ppm, then that's half the dilution or 13%, but you may need to use a supplemental algaecide (PolyQuat 60) or phosphate remover to prevent algae growth. Thanks Richard, Now I see why it is such a problem. (I assume you meant 1ppm FC per day?) Is there any way of calculating the ppm one puck will add to 8000 gallons or 36000 liters

Having experienced a problem with high CYA I am looking at alternative methods of maintaining a clean bright pool. I note that on this forum SWG seems to be favored but in Spain Ionizers seem to be very popular. This company in Spain www.sugar-valley.net/applications/index.php seem to have a multitude of products that together seem to automatically manage everything to do with water balance. I do not live at my house in Spain or I would probably just use liquid chlorine as this seems to be the simplest solution. Instead I have to rely on local 'expertise' which tends to be home grown and tends to be reactive rather than pro active which means that automated systems do have their attractions (and expense!) Does anyone have any views on the relative merits/drawbacks of SWG, Ionizers, algae and pH management and/or combining these as this company seems to have done.

Given that keeping CYA at the right level is such a problem, is there a standard calculation that shows how much water needs to be drained from the pool for each Trichlor puck that is used.

Hi Richard Thanks for your reply and info. The CYA has been this high at least since last Sept when I first tested it with test strips, however, I cant get a very accurate reading as the colour is not identical to any on the colour chart but is closest to 300ppm so its a bit of a guess. I hadn't thought of it before but I will dilute the pool water and retest to see what I get before taking any action. I do have some algaecide in already as a preventative measure and at the moment the FC is off the scale somewhere, probably about 10 or 12ppm, because my pool maintenance guy has had the pump running for 7 hours a day and tabs in both skimmers but I am hoping it will come down soon. I did swim last week though and the water smelt and tasted quite normal. You say that keeping the FC at 15ppm is safe if the CYA is high, I recognise that there is a relationship between the effectiveness of chlorine and CYA but is this the same for red eyes etc? I only ask because this is a rental property and I wouldn't want any punters complaining of bleached hair or peeling skin!! In any case I think I will keep the FC at about 5ppm and use algaecide as you suggest. Mac

Hi, I'm new here but I hope that you can help me with a problem. I have an 8000 gallon pool in the South of Spain that has been behaving itself for 4 years or more. As is the practice in Spain chlorine is administered via Trichlor tablets and water chemistry is checked using OTO test kits. Having read on this forum and others the importance of FC I got hold of some 6in1 test strips. All seems OK with the exception of CYA which seems to be about 300ppm. I recognise that this far from ideal but the refilling of pools is strictly prohibited in Spain due to water shortages. This being the case I have would like to only add chlorine without CYA until the CYA level is reduced through backwashing etc, however, I expect that this will take sometime. From what I have read here I see that high levels of CYA reduce the effectiveness if chlorine which raises a couple of questions: 1. What level of FC would I need to maintain to counteract the high CYA level. 2. What level of FC is safe for swimming