In which order would you tackle redressing this pool imbalance

[SantiSuk]

Mid July I tested my well source water that auto-tops up my pool. I was horrified to find its TDS was 2,600ppm. Had not tested  source waters before, but now I realised why my pool had begun to taste more salty for a constantly maintained TDS level (wrongly assuming that the dissolved solids would be at least 90% salinity) of 3,200ppm and why I was having to rack up the chlorinator's power level to deliver acceptable chlorine levels. Of course rain water naturally dilutes your pool and I measured rain TDS at only 130ppm. By mid July we had received very little rain in lower Sisaket, so the long dry season had obviously led to high TDS levels in my pool - probably about 1,500ppm +/- 500ppm I roughly guesstimated.

 

So in mid August I set about attempting to redress the high TDS levels by using rain water replacement, which meant making sure that the reserve balance tank on my pool was kept at low levels to capture as much rain water as possible - ie pumping out the main pool to waste after a rainstorm to await the next refreshing dollop of god's free water! I switched off the chlorinator and manually dosed chlorine form that point onwardsand began my campaign. I decided not to slavishly maintain the other chemical levels at my preferred levels if they were sort of within range of acceptable.

 

Which is all a long explanation of why I now face a pool with rather imbalanced levels (but not hopelessly imbalanced!). Current levels now that I have achieved a level of rain replacement which has diluted the original largely well water pool down by about 50%* are:
 

Total chlorine 2.5ppm

Free chlorine 2.0ppm (shocking is clearly necessary)

TDS 2,600ppm (I estimate salt content is probably now down to around 2,000ppm)

pH 7.3ppm (rain water is quite acidic at 6.8, so I haven't had a problem with pH in a pool that normally drifts upward in pH)

TA 40ppm, down from my normal maintained levels of 80-100 (rain water has a TA of 20-30 hereabouts)

CyA 55ppm - stabilised chlorine, manually dosed has kept this at satisfactory levels.

 

Question - in which order would you tackle the imbalances of:

1. high combined chlorine levels (need for shocking)

2. salt addition to get up to salt levels of 4,000ppm (I replaced my Astral chlorinator with an Emaux in August and it wants to be maintained at significantly higher salt levels than the previous Astral one)

3. TA - addition of pretty significant quantities of baking soda (maybe up to 10kg, but obviously in stages until levels reach target and recognising that baking soda dosing takes several days to fully show through IME)
 

My inclination would be get the TA right first then the pH then shock then finally loads of salt to get the chlorinator kick-startred. I know that advice is generally to do TA before you do pH, but the rest is guesswork on my part. Any comments? Maybe other prioritisation is not that important?

 

 

*50% is not as good a dilution as I would have hoped for over a 45 day rainy season period (we have had a much drier microclimate rainy season here than I can remember in 6 years). Hoping for more before mid October but I need to get started on rebalancing the pool chemie now. I'll try the same exercise next year and fix up guttering and rainwater catchment to tank from the guest/pool room building roofing to maximise rain capture. Note that because of compounding effects (you are diluting already-diluted water later on in the programme) it is easy to get a good heads start but once you have reached 40% compounded dilution (ie 40% of the poolwater is rainwater it takes a lot more effort to get up to 50% diluted than it did to get up from 0% new rainwater to 10%. Getting up to a compounded dilution level of 80% plus takes a hell of lot of rain!

 

BTW, my well water calcium levels are quite OK at 130ppm - must be some other dissolved junk in the source water! I also have a village piped water supplied which is better than my well water on TDS and calcium (TDS of 1,300ppm) but rainwater is by far preferable on TDS.
 

BTW no 2 - I know I need a meter that measures salinity independently of TDS rather than my cruder (cheaper) TDS-only meter. Waiting for Swimming Pools Thailand to show stock (or my next UK visit)!

 

 

Reference material on why can high TDS levels in pools be a problem

http://www.poolwizard.net/problems/tds.htm

[madmax2]

I do not have a clue what you are talking about but if our PH is to low i put soda ash in the pool to bring it back up to the correct levels

95% of the time its the rain that causes this problem

We took our salt water chlorinator out when it stopped working and just add granulated chlorine to the pool twice a week

The price we were quoted for a new chlorinator would pay for 19 years supply of chlorine. we also save on electricity by running the pump twice a day for 2 hours each time instead of the 8 hours a day we were running it before 

[sappersrest]

SantiSuk I do know the point you are trying to make, if you give me a day or two reply with the consice info you require.  In the short term get your TA up to the correct levels that would be my first action.

[sappersrest]

2 hours ago, madmax2 said:

I do not have a clue what you are talking about but if our PH is to low i put soda ash in the pool to bring it back up to the correct levels

95% of the time its the rain that causes this problem

We took our salt water chlorinator out when it stopped working and just add granulated chlorine to the pool twice a week

The price we were quoted for a new chlorinator would pay for 19 years supply of chlorine. we also save on electricity by running the pump twice a day for 2 hours each time instead of the 8 hours a day we were running it before 

 

The guy is obviously very passionate about his pool water chemistry and wishes to get it correct.

try doing some research on the langelier saturation index  for keeping swimming pool water in balance, or the Palin index.

As I have stated numerous times on this forum pool water balance is not about just keeping the correct levels of chlorine and the pH correct

[SantiSuk]

19 hours ago, madmax2 said:

I do not have a clue what you are talking about but if our PH is to low i put soda ash in the pool to bring it back up to the correct levels

95% of the time its the rain that causes this problem

We took our salt water chlorinator out when it stopped working and just add granulated chlorine to the pool twice a week

The price we were quoted for a new chlorinator would pay for 19 years supply of chlorine. we also save on electricity by running the pump twice a day for 2 hours each time instead of the 8 hours a day we were running it before 

Agree with your comment about the purely financial case for a chlorinator. I ran my pool both with manually dosed chlorine for a couple of years and then with a chlorinator for the last 4. I still switch off the chlorinator and manually does with chlorine during the rainy season (to get a cyanauric acid booster that obviates/reduces the need for buying CYA powder).

 

It does depend on the size of your pool - a new chlorinator for my 90 cu.m pool cost ThB 35,000 recently and when I was manually chlorinating I would roughly speaking use a 50kg tub of chlorine powder a year at say ThB 5,000. So that's a 7 year rather than 19 year 'crude payback'; a pool half that size would be 14 years though. I say "crude" payback as there are many other cost factors that feature in and go either way - the cost of salt, cost of CYA powder, differential water testing costs, price of labour if you are using pool boys etc. Whichever way you cut it the claims by some that chlorinators are cheaper financially than manual dosing are questionable at best and tend to ignore capital costs and the replacement costs of cells.

 

That said, personally I still prefer the chlorinator route for the consistency of chlorine levels it provides - I find that when manually dosing I sometimes get lazy and delay a dose or I'm away unexpectedly and pool boy (brother-in-law) doesn't do what he's supposed to. Consistent levels have removed the need for sweeping blobs (small) of emerging green algae off the floor and scrubbing emerging green from the (limited areas of) grouting which used to irritate me. It was not a regular feature when I was manual dosing - maybe once every couple of months - but still a boring chore - as is sticking chlorine in a couple of times a week at least (salt dosing I do monthly - loading the pool with a couple more bags than you actually need for short term levels does not result in over-chlorination as you can adjust the chlorinator power).

 

But there I go again being all anal! Or as Sappersrest so politely puts it "passionate" (thanks for that Sappersrest )

Edited October 3, 2016 by SantiSuk

[sappersrest]

Total dissolved solids in swimming pools TDS

 

Total dissolved solids is a measurement of everything that has ever dissolved in your swimming pool water. This includes minerals that separate from your pool chemicals, such as calcium and sodium sulphates sulphides and phosphates plus others to name a few., and every bit of dissolved dust, pollen, swimmer waste, algae remains – everything!

Distilled water has a TDS level of 0, drinking water has a TDS of under 500 ppm, and sea water can be as high as 35000, but what about pool water?

 

TDS levels in swimming pool water a historic change of practice.

There are varying opinions on what level of total dissolved solids is too high for swimming pools. Since the early 1970s the following was observed, levels of 1500 ppm or above was deemed too high,. Of course this lead to dumping of a lot of water to reduce TDS this practice was followed to the letter in public pools through Europe and also the same advice was given to home owners as well.

The main reason was the langellier saturation index was  used to calculate if the water was corrosive or not. This index takes into account the level of TDS. Now at that time this was very important for for pool equipment pumps, heat exchangers , all commercial pools at that time had steel filters, as corrosion of the equipment and pool fabric was becoming more problematical  So the TDS levels were kept below 1500 ppm.

 

Now we move on to the late 1990s

Pool professionals  and chemists after doing some research , came to the conclusion the 1500 ppm figure was too low so as to be practical and the bar was raised to 1000ppm above source water, to a max of 3000 ppm as equipment is more corrosion ressistant.

 

Since then in 2015 a new guidance was given that TDS should be no greater than 1000 ppm above source water and sulphates should be no greater than 360 ppm.

 

How does that effect us in Thailand?

For those who do not have salt pools , the above is very important as a myriad of chemicals are used in the day to day running of the pool all of which will affect the TDS of the pool and the inherent problems that is caused by high TDS.

 

Salt pools

 

You will have to live with high TDS

Salt pools, those that use salt chlorine generators, routinely operate with a salt level of over 3500 ppm so if your source water has a high TDS coupled with the fact that Ph adjusting and TA chemicals will add to it ,you should operate a regime of dilution not so much as you will dump the salt donor in the pool but enough to keep the high TDS at bay .Normal backwashing should suffice.

Though not scientific you will be able to tell by the extra salty taste of the water coupled with sore eyes and itchy skin.

 

For salt pool use the Palin method to determine balanced water

 

 

 

 

How to test pool water for TDS

Testing for TDS in pools is best checked for with a digital test meter that measures the conductivity of the water to more accurately detect dissolved particles. Aquachek makes a TDS test strip which should be accurate enough for most applications.

 

 

So quick recap for non salt pools 1000ppm above source water.

For salt pools high TDS but not so high the water tastes crap.

 

 

[sappersrest]

"Total chlorine 2.5ppm

It is combined chlorine you should be  testing i.e.  total chlorine 2.5 ppm minus free chlorine2.0 ppm gives you you a combined chlorine of  0.5ppm which is good

 

Free chlorine 2.0ppm (shocking is clearly necessary) 

Why if your pool looks good why add more (with really good management you could even get down lower  ,after all you want to swim in water not chlorine. 

 

TDS 2,600ppm (I estimate salt content is probably now down to around 2,000ppm

You are really going to have to live with it, and it will go higher once you add salt.

 

pH 7.3ppm (rain water is quite acidic at 6.8, so I haven't had a problem with pH in a pool that normally drifts upward in pH)

Try to get you pH down to 7.2  the killing power of chlorine is 20 percent greater than at 7.4

 

TA 40ppm, down from my normal maintained levels of 80-100 (rain water has a TA of 20-30 hereabouts)

You know what you are doing with that

 

CyA 55ppm - stabilised chlorine, manually dosed has kept this at satisfactory levels."

Absolutly fine.

 

any more info pm me.

 

[madmax2]

7 hours ago, SantiSuk said:

Agree with your comment about the purely financial case for a chlorinator. I ran my pool both with manually dosed chlorine for a couple of years and then with a chlorinator for the last 4. I still switch off the chlorinator and manually does with chlorine during the rainy season (to get a cyanauric acid booster that obviates/reduces the need for buying CYA powder).

 

It does depend on the size of your pool - a new chlorinator for my 90 cu.m pool cost ThB 35,000 recently and when I was manually chlorinating I would roughly speaking use a 50kg tub of chlorine powder a year at say ThB 5,000. So that's a 7 year rather than 19 year 'crude payback'; a pool half that size would be 14 years though. I say "crude" payback as there are many other cost factors that feature in and go either way - the cost of salt, cost of CYA powder, differential water testing costs, price of labour if you are using pool boys etc. Whichever way you cut it the claims by some that chlorinators are cheaper financially than manual dosing are questionable at best and tend to ignore capital costs and the replacement costs of cells.

 

That said, personally I still prefer the chlorinator route for the consistency of chlorine levels it provides - I find that when manually dosing I sometimes get lazy and delay a dose or I'm away unexpectedly and pool boy (brother-in-law) doesn't do what he's supposed to. Consistent levels have removed the need for sweeping blobs (small) of emerging green algae off the floor and scrubbing emerging green from the (limited areas of) grouting which used to irritate me. It was not a regular feature when I was manual dosing - maybe once every couple of months - but still a boring chore - as is sticking chlorine in a couple of times a week at least (salt dosing I do monthly - loading the pool with a couple more bags than you actually need for short term levels does not result in over-chlorination as you can adjust the chlorinator power).

 

But there I go again being all anal! Or as Sappersrest so politely puts it "passionate" (thanks for that Sappersrest )

I was quoted 65K baht for a new salt water chlorinator at the time, and i still only pay 3600 baht for 50 kg of 90% granulated chlorine  at present, it was slightly cheaper before , it pays to shop around, so approx 19 years running costs is right for our pool without taking into account the saved electricity   

[SantiSuk]

Where did I say you were wrong?