Dichlor (The Dirty Little Secret)

[Hillbilly Hot Tub]

I started using bleach in my pool along with trichlor about four or five years ago.  I started with bleach (along with dichlor) in my spa about two years ago after five years with dichlor or a combination of dichlor, N2 or Frog and ozone.  In my situation being a daily user, bleach after using dichlor to reach the proper CYA level has worked best.  It is not the easiest and it is not for everyone, but it is certainly not difficult.  I now use chlorine only, no minerals, no ozone.  I shock weekly with MPS because I like how it works.  I use the small 24 oz bottles of regular Clorox which are easy to handle and are as small as my dichlor container.  Every other week I may need to add a tablespoon of dry acid for pH but thats about it.  I don't use borates or anything like that and I keep it simple.

[glow]The advantage to bleach[/glow], IMO, is of course no CYA and [glow]the lack of TDS.[/glow]  The water does not bog down.  It has the fresh fill feel for months.  Even though my water was always crystal clear with dichlor, it would slowly go downhill.  At my four month water change, there was always that...there's nothing like fresh water...realization.  Not so with bleach.

I am not one to recommend bleach to anyone, but you need not fear it either.  While it may not be for everyone, it works, works well and is probably as pure a chlorine as is practical to use.  

TDS is increased with bleach by quite a bit. It is a salt. If it is more/less than the additives, I don't know, just did not want people to think it did not raise the TDS.

[chem geek]

The TDS added by bleach, chlorinating liquid, and lithium hypochlorite is salt -- sodium chloride.  Upon addition, for every 10 ppm FC that is added, it also increases the salt by 8 ppm.  Dichlor does not add salt upon addition, but does increase TDS in the form of CYA where for every 10 ppm FC that is added it also increases CYA by 9 ppm.  All sources of chlorine also add to chloride (salt) when the chlorine gets consumed/used and that is also at the rate where for every 10 ppm FC you end up with 8 ppm salt.

So the net result is that bleach, chlorinating liquid, and lithium hypochlorite build up TDS in the form of salt twice as fast as Dichlor.  However, salt is pretty innocuous and it takes a very large buildup before it becomes a problem.  This is not the case for Cyanuric Acid (CYA) where far smaller amounts affect the chlorine effectiveness.  Higher salt levels do not affect the chlorine effectiveness.

At 4 ppm FC per day chlorine usage, after 3 months using bleach, chlorinating liquid or lithium hypochlorite, you increase salt by 576 ppm.
If you use Dichlor instead, then you increase salt by 288 ppm and increase CYA by 324 ppm.

Basically, the "bleach increases TDS faster" is a true statement of little importance since you change the water in the spa long before this becomes an issue.  In other words, it is what TDS is composed of that matters -- TDS by itself is a non-issue unless it gets extremely high (many thousdands of ppm) such as in saltwater chlorine generator pools where the salt level is around 3000 ppm and the TDS is around 3200 ppm as a result.

Richard

[Hillbilly Hot Tub]

Its not a huge thing, I was just pointing out that there is not a lack of TDS with bleach. The recommended TDS is not to exceed 1500 ppm higher than what the fresh start water was. The is no minimum or maximum. Excessively high TDS will cause the water to look dull or tired and may have a bad or salty taste, not that you should be drinking your spa water! As TDS increases above 2000 ppm, there is a greater probability of galvanic corrosion when there are dissimilar metals within the system such as if you have a copper heat exchanger and other metals in the plumbing, then galvanic corrosion can occur. (NSPf certified pool operator handbook 2007 edition)

No matter how you look at it, frequent water changes will stop many issues, those who can not due to water constaints need to be careful....

[In Canada eh]

Basically, the "bleach increases TDS faster" is a true statement of little importance since you change the water in the spa long before this becomes an issue.  

Would this statement not apply to dichlor also. Meaning you change the water long before the increase in CYA matters


Just a thought

[chem geek]

Would this statement not apply to dichlor also. Meaning you change the water long before the increase in CYA matters


Just a thought

The difference is that 300 ppm of salt means nothing while 300 ppm of CYA means a lot -- relative to 30 ppm CYA, a CYA of 300 ppm reduces chlorine's active concentration (hypochlorous acid) by a factor of 10.  The increase in salt doesn't do anything, until as HHH points out the salt level gets rather high.

As I posted above, at 4 ppm FC per day chlorine usage, after 3 months using bleach, chlorinating liquid or lithium hypochlorite, you increase salt by 576 ppm.  If you use Dichlor instead, then you increase salt by 288 ppm and increase CYA by 324 ppm.  It would take almost 8 months of not changing the water for the bleach to accumulate 1500 ppm of salt above the initial fill amount.  There is no way you could go that long using Dichlor at the 4 ppm FC per day usage.

Am I not being clear about this?  With the bleach you are accumulating an extra 288 ppm of salt (above and beyond the 288 ppm salt that Dichlor would add) in 3 months (at the aforementioned chlorine usage) and that is negligible.  The 324 ppm of CYA from Dichlor is not negligible and has a significant effect on the active chlorine concentration, even after the first month when the CYA builds up to 108 ppm reducing chlorine's effectiveness by a factor of 3 relative to 30 ppm CYA.

Can someone offer a better way of explaining this since apparently I'm not communicating this very effectively?

[Nitro]

Can someone offer a better way of explaining this since apparently I'm not communicating this very effectively?

How about this?  

[Tman122]

How about this?  

That explains it but the title!! It's not a secret and it's not dirty!! Dichlor has worker for thousands and thousands of people for many many years.

[brian_tr]

I am draning my tub today due to high CYA.  I been fighting cloudy water and itch.  Had forgot about CYA.  When checked it is very high.  Been about 3 months since water change which I was due anyhow.  I use the tub almost everyday and shock with Dichlor once a week.  I am tempted to try the bleach method.  Currently I use a pill box for my Dichlor to hold a weeks worth.  What would be good for bleach if I decide to use it?  

My TA is over 400 from tap and will be trying Nitro's way to lower it.  Usually this is a two week battle to get down.

[Chas]

My TA is also high from the tap - I have a 500 gallon tub. Every time I change my water (twice a year most of the time) I add four ounces of Spa Down, run the spa for several hours, then add four more. That usually brings my TA and pH close enough to go ahead and chlorinate and begin using. I may have to add another ounce later in the week, but no battle, no trouble.

And if you want to use less Dichlor, you could try shocking once per month instead, or if you like to shock every week, shock with a non-chlorine oxidizer product such as MPS, Renew, etc.

You could try a Nature2 cartridge to lower the amount of chlorine you need to add - it works best with a daily dose of MPS.

Lots of options.

 8-)

[chem geek]

What would be good for bleach if I decide to use it?

If you do decide to use Dichlor-then-bleach, then the best bleach to use is Clorox Regular unscented since it has the least amount of "excess lye" in it.  It says "6% Sodium Hypochlorite" in the ingredients and also says "5.7% Available Chlorine" because it is registered with the EPA as a disinfectant for use in swimming pools.

The method Chas describes for lowering the TA is similar to Nitro's method since it involves acid addition with aeration.  4 ounces (volume) of Spa Down in 500 gallons with an initial TA of 400 ppm would lower the pH from 7.5 to 7.0 and the TA by 35 ppm to 365 ppm.  Aeration raises the pH back up.  Repeating this again lowers the pH to 6.7 and the TA to 330 ppm.

Given that 4 ounces of dry acid in 500 gallons lowers the TA by 35 ppm, perhaps the initial TA isn't so high (Chas, what is the "high TA" you initially have in your spa?).  If the initial pH were 8.0 and TA 200, then the 4 ounces of dry acid in 500 gallons would lower the pH to 6.8 and TA to 165 ppm.  Repeating this would get the TA to 130 ppm.

[Chas]

(Chas, what is the "high TA" you initially have in your spa?).

I haven't tested it in years - typical "do as I say, not as I do" spa dealer... but a quick dip of a test strip in the kitchen sink reveals off the scale on the high side for both pH and TA. The test strips I have top out at 180 for TA. I think the last time I took it into the store and ran it through the chem lab (Pinpoint) it was just over 200, but not over 300.

When we opened our third ( and now only ) store, it was fed by well water. That was amazingly high on both pH and TA - and hardness. I filled our first spa, tossed in a little spa down and went home. We came in the next day and the tub was calcified. It took close to a pound of Spa Down to bring it right, and I shut off the heater and circ pump until it got close! Embarrassing! We finally got all the calcium to go back into solution, took three or four days, then drained and refilled it. This time we hit it with Pool Acid right from the start. Since then we have connected the building to city water, no more problems.

And I don't recommend liquid acid except in emergencies.

 8-)

[Nitro]

I am tempted to try the bleach method.

If you do use the Dichlor/Bleach method, lower your TA to 50-60 ppm, and consider adding Borates. That will keep your pH in range. I would add Borates even if I wasn't using bleach. The water feels nice and silky afterward.

My TA is over 400 from tap and will be trying Nitro's way to lower it.  Usually this is a two week battle to get down.

I lowered a tub's TA from ~450 to 60 in just a few hours using that method. What's nice is you don't have to guess how much acid to add each aeration cycle. It's easy to calculate it.

Let us know how it works out.

[tony]

The difference is that 300 ppm of salt means nothing while 300 ppm of CYA means a lot -- relative to 30 ppm CYA, a CYA of 300 ppm reduces chlorine's active concentration (hypochlorous acid) by a factor of 10.  The increase in salt doesn't do anything, until as HHH points out the salt level gets rather high.

As I posted above, at 4 ppm FC per day chlorine usage, after 3 months using bleach, chlorinating liquid or lithium hypochlorite, you increase salt by 576 ppm.  If you use Dichlor instead, then you increase salt by 288 ppm and increase CYA by 324 ppm.  It would take almost 8 months of not changing the water for the bleach to accumulate 1500 ppm of salt above the initial fill amount.  There is no way you could go that long using Dichlor at the 4 ppm FC per day usage.

Am I not being clear about this?  With the bleach you are accumulating an extra 288 ppm of salt (above and beyond the 288 ppm salt that Dichlor would add) in 3 months (at the aforementioned chlorine usage) and that is negligible.  The 324 ppm of CYA from Dichlor is not negligible and has a significant effect on the active chlorine concentration, even after the first month when the CYA builds up to 108 ppm reducing chlorine's effectiveness by a factor of 3 relative to 30 ppm CYA.

Can someone offer a better way of explaining this since apparently I'm not communicating this very effectively?

There is good TDS (salt) and there is bad TDS (most everything else).  CYA is TDS and a chlorine inhibitor so it contributes in two ways to the deterioration of water.  Salt at this level has a zero consequence.  It is a small fraction of the salt by volume and concentration that is added to water for a Salt Water Generator that is so popular with pools and now starting with spas.

[tony]

I haven't tested it in years - typical "do as I say, not as I do" spa dealer... but a quick dip of a test strip in the kitchen sink reveals off the scale on the high side for both pH and TA. The test strips I have top out at 180 for TA. I think the last time I took it into the store and ran it through the chem lab (Pinpoint) it was just over 200, but not over 300.

When we opened our third ( and now only ) store, it was fed by well water. That was amazingly high on both pH and TA - and hardness. I filled our first spa, tossed in a little spa down and went home. We came in the next day and the tub was calcified. It took close to a pound of Spa Down to bring it right, and I shut off the heater and circ pump until it got close! Embarrassing! We finally got all the calcium to go back into solution, took three or four days, then drained and refilled it. This time we hit it with Pool Acid right from the start. Since then we have connected the building to city water, no more problems.

And I don't recommend liquid acid except in emergencies.

 8-)

Chas, this issue comes up on the forums on a regular basis.  It would be nice to have your fix for a calcified spa.  Many people try to scrub the calcium off but doing it chemically seems to be the correct way.