Total Alkalinity

[nontabury]

The Total Alkalinity in my concrete pool was very low,about 50ppm, so I started to add sodium bicarbonate,at the same time adding acid to keep the ph down,unfortunatly the ALkalinity level went down slightly . This month I've only added Sodium Bicarbonate,no Acid, thinking to myself

if I can get the Alkalinity correct, I will then focus on the PH, the result, my Alkalinity has gone down to about 15ppm. What am I doing wrong?.

[nontabury]

No replies

[curtklay]

You are probably not adding enough bicarb. It takes 1.5 lb to raise alkalinity 10ppm in a pool with 10,000 gallons. Find out how many gallons your pool is, and add enough to get you between 80-100 ppm. Probably at least 10 lbs for an average pool. If you're down to 15ppm, it will take a lot more. Broadcast the bicarb into the pool with pump running. Don't add any acid until you have the alkalinity up to standard. Then lower the PH if needed, while keeping your eye on the alkalinity. It will take some juggling, but you should be able to reach 80-100ppm alkalinity and a 7.4-7.6 PH. Check both weekly, and keep them in this range.

[SantiSuk]

You are probably not adding enough bicarb. It takes 1.5 lb to raise alkalinity 10ppm in a pool with 10,000 gallons. Find out how many gallons your pool is, and add enough to get you between 80-100 ppm. Probably at least 10 lbs for an average pool. If you're down to 15ppm, it will take a lot more. Broadcast the bicarb into the pool with pump running. Don't add any acid until you have the alkalinity up to standard. Then lower the PH if needed, while keeping your eye on the alkalinity. It will take some juggling, but you should be able to reach 80-100ppm alkalinity and a 7.4-7.6 PH. Check both weekly, and keep them in this range.

I read this advice on technique somewhere on the internet from a guy who claimed to maintain YMCA pools.

"While your filtration system is off and the water is motionless, stand in the deep end of the pool and sprinkle (don't dump the product or go too fast), the Sodium Bicarbonate or Alkalinity Up. Allow the water to sit for 2-3 hours, then turn the pump back on and allow the pool to fully circulate, usually 4-6 hours, then re-test your pool's alkalinity balance. Doing this technique will increase your alkalinity without much happening to the pH level."

I have not yet tried it. Indeed my pool has tended to alkaline for its first year of operationhas but turned to the acidic side in the last month. It may be the rainstorms (since the rainwater and my well water is on the acidic side) or more likely Total Alkalinity has fallen (I have noticed that my pool's chlorine consumption has doubled in recent months). Am waiting to get a Total Alkalinity test kit and then will get cracking when I get back from the UK in 3 weeks time.

Meanwhile, before I set off for the UK I would like at least reduce the acidity level/raise ph. The pool equipment installer left a sack of Soda Ash (Sodium Carbonate, which I gather is different to Sodium Bicarbonate/Baking Soda and will address acidity but not tackle the Total Alkalinity problem if there is one).

Does anyone know a sensible try-it-retest-redoseasnecessary level for a 20,000 gallon pool, using soda ash?

[SantiSuk]

And another thing I read about raising Total Alkalinity:

"You should only add sodium bicarbonate at the rate of 1 kg per 50,000 litres of water every 4 days. Raising the TA can therefore be quite a time-consuming, slow process"

Source: http://www.havuz.org/pool_pool/pool_maintenance/water_testing/total_alkalinity.htm

[curtklay]

You are probably not adding enough bicarb. It takes 1.5 lb to raise alkalinity 10ppm in a pool with 10,000 gallons. Find out how many gallons your pool is, and add enough to get you between 80-100 ppm. Probably at least 10 lbs for an average pool. If you're down to 15ppm, it will take a lot more. Broadcast the bicarb into the pool with pump running. Don't add any acid until you have the alkalinity up to standard. Then lower the PH if needed, while keeping your eye on the alkalinity. It will take some juggling, but you should be able to reach 80-100ppm alkalinity and a 7.4-7.6 PH. Check both weekly, and keep them in this range.

I read this advice on technique somewhere on the internet from a guy who claimed to maintain YMCA pools.

"While your filtration system is off and the water is motionless, stand in the deep end of the pool and sprinkle (don't dump the product or go too fast), the Sodium Bicarbonate or Alkalinity Up. Allow the water to sit for 2-3 hours, then turn the pump back on and allow the pool to fully circulate, usually 4-6 hours, then re-test your pool's alkalinity balance. Doing this technique will increase your alkalinity without much happening to the pH level."

I have not yet tried it. Indeed my pool has tended to alkaline for its first year of operationhas but turned to the acidic side in the last month. It may be the rainstorms (since the rainwater and my well water is on the acidic side) or more likely Total Alkalinity has fallen (I have noticed that my pool's chlorine consumption has doubled in recent months). Am waiting to get a Total Alkalinity test kit and then will get cracking when I get back from the UK in 3 weeks time.

Meanwhile, before I set off for the UK I would like at least reduce the acidity level/raise ph. The pool equipment installer left a sack of Soda Ash (Sodium Carbonate, which I gather is different to Sodium Bicarbonate/Baking Soda and will address acidity but not tackle the Total Alkalinity problem if there is one).

Does anyone know a sensible try-it-retest-redoseasnecessary level for a 20,000 gallon pool, using soda ash?

Use your PH test kit to determine how low the PH is. Add soda ash 1 lb. at a time, recheck the next day, and repeat the application as needed until you reach 7.4 to 7.6. But you really need to adjust the alkalinity first. If the alkalinity is low, the PH won't stabilize, giving you readings that tend to bounce up and down. Rain water is acidic. Your chlorine consumption is increased due to low PH. If the PH is low, the alkalinity is almost certainly low as well. The rule is adjust alkalinity first, then recheck PH. A good test kit is your best tool.

[SantiSuk]

Many thanks for the confirmations, Curtklay. Yes- I realised I should raise the alkalinity first, but live in the wilds and can't access kit with TA capability before I go away (will buy some slightly more sophisticated kit than my hitherto 'red and yellow pots' in UK and bring back). I've been lulled into a false sense of security hitherto by a pool that behaved itself remarkably with just a bit of chlorine twice a week and some acid once a week.

With the potential need now to address TA, maybe I'll take a punt and do a modest bicarb dosing to raise that TA level anyway and leave it for a couple of days, then use the soda ash to raise the pH.

Does Tesco sell bicarb in large enough packs to be useful for a swimming pool dose?

After a couple of weeks away I'm going to have to do my usual recovery job on the pool anyway as my BIL never does what I pay him to do!

[curtklay]

Adding some extra bicarb won't do any harm. Any time you add acid to the pool, you can expect alkalinity to gradually drop. Adding bicarb will be regular maintenance. Not sure about quantities available at Tesco. Maybe they can order it? Next time you hit the big city, I would get a 10 lb. bucket at a pool store to have on hand.

BTW, I don't agree with the 4 day period of raising alkalinity. Yes, it can be a slow process, but in pools that were down very low, I have added 10 lbs at one time and more over the next few days with successful results. I worked in the pool industry in California for 25 years, and never heard of waiting 4 days between applications of bicarb. (and unless your pool is very shallow, I wouldn't stand in the deep end)

For your 20,000 gallon pool, you can expect 3 lbs. of bicarb to raise your alkalinity 10ppm. You could add that daily, rechecking with your test kit until you reach 80-120ppm.

When you get an alkalinity tester, you may be surprised at how low it has gotten. But if the water is clear, and not acidic enough to burn your eyes or skin, you should be able to get it in balance without too much trouble. And you should see a reduction in chlorine consumption.

[nontabury]

My Pool is 65000 lts, so last month I was adding 1.5kg of sodium bio card every 4 days, this I did

On about 5 occasions. But strangly the alkality went down, now I have started to drop in, as apposed to

Sprinkle in, 3 kg every 2 days. This I am doing in the hope of shocking the pool. Not sure how much in total I will need to add and for how long,but according to the calculations on a pool web site, it's going to take a very large quantity

[curtklay]

3 kg. every 2 days is about right for your pool. The total required will depend on how low your alkalinity is. If it's still at 15ppm as you earlier stated, it's going to take about 10 kg. It's normal for a new pool to have a large acid demand for a while, then taper off as the plaster/gunite/cement cures. At that stage, your routine maintenance will change to smaller amounts of acid to lower PH weekly. The acid will also lower alkalinity which must be brought back up to stabilize the PH. Raising alkalinity is an ongoing chore as it tends to drop naturally, and with acid additions. But once you get it up to 80-120ppm, it will be easier to keep it there with weekly additions of bicarb. When it drops very low, it's harder to get it back up and takes large quantities of bicarb, added over time, to do so. The bicarb should be broadcast over the pool surface, not dumped in.

Normal maintenance of a plaster pool over 1 year old usually consists of weekly additions of small amounts of acid to lower PH, weekly additions of bicarb to raise alkalinity, (I know this sounds counterproductive, but that's how it is) and shocking every 2 weeks. Your test kit is your best friend, and once you find the pattern for your pool, it will become routine.

Shocking is not done with sodium bicarb. It is accomplished with large doses of fast dissolving chlorine, liquid or granular.

[SantiSuk]

....... Not sure about quantities available at Tesco. Maybe they can order it? Next time you hit the big city, I would get a 10 lb. bucket at a pool store to have on hand. ...............

BTW, Tesco do sell sodium bicarb. Yes - it's small scale but at 10baht for a 300gram pack it is substantially cheaper than a pool shop. The pack is actually a very handy zip-locked 300 gram pouch, making the contents easy to spread and for which I can already see re-uses. Filling with chlorine granules/powder to leave for pool boy (BIL) when I'm away being the most obvious!

Apologies to those around where I live for having cleared the shelves (left a few for the serious baker) - hope they have restocked by now

PS I know you wouldn't, Curtclay, but for the uninitiated like me, do buy the Baking Soda packet (pure sodium bicarbonate) and not the very similarly packaged Baking Powder (Baking powder contains sodium bicarbonate, but also includes the acidifying agent, cream of tartar. I guess that would at least partly defeat the object of increasing the alkalinity of your pool).

I bought Total Alkalinity test tablets in the UK - £14 for 250, which are easy to use and should last me several years (or maybe they'll go off - PM me if anyone is desperate for a few - kits here that include TA are quite expensive). So now I'm fit to go. Having dosed the pool with 3 kg before I left for the UK I find that the pool is at 60 on return, so it must have been pretty low when I started the reparations of alkalinity balance. Another few kilos over the next few days should do it.

[robertsonmartin]

Have a look at the shared media file which is a good pool manager handbook. It has tables at the back to show what quantities of chemicals to use depending on what you want to raise or lower per pool size. It might help a few people.

Pool Manager Handbook (LaMotte).pdf