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Strict Standards: Non-static method utf_normalizer::nfkc() should not be called statically in /home/havuzorg/poolforum/includes/utf/utf_tools.php on line 1663

Strict Standards: Non-static method utf_normalizer::nfkc() should not be called statically in /home/havuzorg/poolforum/includes/utf/utf_tools.php on line 1663

Strict Standards: Non-static method utf_normalizer::nfkc() should not be called statically in /home/havuzorg/poolforum/includes/utf/utf_tools.php on line 1663
soft water make up - Swimming Pool Help

soft water make up

Total hardness and calcium hardness in pool water. Scale, calcium buldup, hard water and scaling problems in swimming pools.

soft water make up

Postby Dan R » Mon 27 Feb, 2006 15:43

Great forums here, very helpful!! I have seen some topics that have raised more questions, but for now...

My question is this: I have always gone by, if the pool is filled with soft water, you are begging for trouble. I understand water is "thirsty" and will seek things out to balance itself, like for instance, lack of calcium in the water, it will find it elsewhere, like from the plaster? Thus causing damage?

So, if the above is accurate, why not can one fill there pool with soft water in the event that the pool is on a salt/chlorine generating system. Like home water softeners, the calcium molecule is replaced by the sodium or sometimes potassium molecule, so would that make the water not "thirsty" anymore thus resulting in a lack of damage to the plaster? Seems to me logical, but I am no water balance scientist!

This is really bugging me, anyone have any comments or facts about this?

Thanks much!!
Dan R
 

Soft water problems

Postby Larry » Mon 27 Feb, 2006 16:05

Welcome to the forums Dan.

Your assumptions are absolutely correct. The reason we emphasise calcium hardness in swimming pool water is that naturally occuring hardness in fresh water is mostly a result of calcium. Also the nature of pool construction means the water is able to leach the calcium from the calcium carbonate found in concrete, plaster and tile grout.

The hardness level of water is made up of a variety of minerals, including magnesium, potassium and of course sodium. In fact the most common complaint of pool owners using salt water chlorine generators is scale.

Soft water can be conditioned using salt if you install a chlorine generator, but for fresh water pools adding cacium in the form of calcium chloride is the easiest, cheapest and quickest way.

So in conclusion, it is not important which minerals are responsible for the water hardness level, but it is actually the level of the total hardness that is of prime importance in pool water balance.

Looking forward to more of your insights Dan.
Larry
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soft water make up

Postby Dan R » Tue 28 Feb, 2006 00:09

Now the gears are spinning... So, if one has a pool that tends to end up with high calcium levels, like an indoor pool that stays real clean thus results in the typical home owner not back washing much because filter pressure never goes up, and they want a solution to high calcium hardness levels and are willing to spend the money on putting a softener on the make up water line, they would be golden if they had a chlorine generator and an adequate supply of sodium in the water? Man, that was a long sentence… Anyway, it’s been a 12 hour day and I am tired in a big way.

Bottom line, if you replace calcium with sodium in a pool, you are safe from the effects of low to no calcium in the water?

By the way, thank you for the speedy response... I will be spending some more time in these forums, clearly, (bad pun), I need some refreshing on my water balance skills.
Dan R
 

*light bulbs above me head*

Postby Dan R » Tue 28 Feb, 2006 00:18

I was just sitting here thinking about this and it came to me... Every Langlier calc I have ever touched calls for a calcium hardness number to calculate the end result, not a total hardness number. So, I have always just focused on Calcium... So it is more important to look at total hardness in this case but in most other cases it's fine to run the calcium numbers?
Got ORP? :-)
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Water softener

Postby Larry » Tue 28 Feb, 2006 06:37

Well Dan, as you have implied, using a softener doesn't reduce the hardness levels in salt water pools by the very nature of their working principle.

An ion exchange mineral, typically a resin, adsorbs calcium and releases sodium (which comes from the salt brine regeneration). The resin has a greater affinity for sodium so will only adsorb calcium when there is no sodium present. But the pool water is salty, so the softener will never "use up" the sodium and get round to dealing with the calcium. Any calcium that is trapped will be displaced by the next sodium ion to happen by.

Hard water is typically treated with a chelating agent to render the calcium inactive. It actually bonds with the calcium ion, keeping it in solution and prevents it from plating out as scale.

Using a water softener on the make up water line will reduce the risk of hard pool water. Close monitoring of the pool water hardness to make sure the hardness is not too low must still be done.

One of the most common sources of hardness in indoor pools not exposed to sunlight is the calcium hypochlorite (non-stabilized "shock" chlorine). If the pool uses cal hypo, regular backwashing is necessary. In the case of a salt water chlorine generator, the hardness will be a result of the salt and the fill water as you mentioned.

The Langelier Index was developed before the advent of salt water systems. At that time hardness was most easily and economically measured as calcium hardness. Nowadays test kits for total hardness are readily available and most test strips show total hardness only. The Langelier calculations can effectively be done using the total hardness value. I remember reading something about the correlation between calcium hardness and total hardness in the Langelier Index. I'll try to find it and post the details here.
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Total hardness vs calcium hardness

Postby Larry » Tue 28 Feb, 2006 07:20

Found it!

Typically total hardness=calcium hardness x 1.18

Looking through the reference books again I see the calcium is "required" chemically to create calcium carbonate (CaCO3) to ensure saturation. If we remove all the calcium in a sodium-rich environment, it would make sense that we may end up with an abundance of sodium carbonate (pH up) or sodium bicarbonate (alkalinity up).

So by removing the calcium that "stabilizes" the carbonate ions, we would end up with water having high pH, alkalinity or both. Perhaps a water chemistry specialist could comment on this.

It is the calcium carbonate that causes scale in hard water, but it seems we still need a certain concentration in the pool.
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Postby Dan R » Tue 28 Feb, 2006 09:13

I can't thank you enough for the time you have spent on this and for sharing your insight. If you are not a "water chemistry specialist", I don't know who is!

Years ago, I had the pleasure of working with a fine water chemist from time to time, I have lost contact with him as we both stopped working at the same company. I am sure he would have something to say about this subject. Bob Edelson is his name, maybe you have heard of him or seen him around a trade show or what not?

Anyway, again, thanks so much!
Got ORP? :-)
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No problem

Postby Larry » Tue 28 Feb, 2006 12:38

Thank you for getting me to focus on and refresh stuff I seem to be forgetting.

Hope to see you at the forums more often.

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Soft water make up

Postby elrey » Wed 03 Jun, 2009 16:27

Is it okay to introduce soften water spplemental makeup in to a chlorinated pool, if the pool chemist can chemically balance the water quality?
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soft water make up

Postby mwwh2o » Fri 29 Jul, 2011 18:27

I would suggest filling the pool initially with hard water then using the water softener for make-up water. As water evaporates, the calcium in the hard water will remain in the pool because it exists as a dissolved solid. If hard water is always used for make-up water, the hardness levels can will get extremely high as more water evaporates and more hard water is added in. I have seen pools with hardness levels of 150 grains or 2500 parts per million which will make your hair stand on end and scale the pool horribly! So, with the pool being filled up with soft water make-up only, the sodium in the soft water means nothing. The salt water pool will have 3000 to 3500 parts per millon or milligrams per liter (they are the same) of Sodium Chloride in it to make the chlorine generator work correctly. Maintaining a consistant level of calcium from the original fill will stop the hardness levels from climbing and reduce scale. What scale is caused by the sodium will be easy to clean off.
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