Shocking with MPS

[Gomboman]

I typically shock with dichlor but the other night I used MPS. My TC level was around .5 ppm before I shocked. I used the MPS that came with my HS starter kit. I believe it's buffered since they recommend using 3 TBS per 250 Gallons. My spa is 450 Gallons so I used 5 TBS. I also added 1 TBS of dichlor to get some sanitizing power.

Anyway, tonight I checked my FC and it was around .5 ppm and my TC reading was 3 ppm. My water smells fine and believe the MPS did it's job. I've used MPS a few other times and had the same problem. I used a K-2005 Taylor test kit. Is it possible for MPS to give you a false TC reading?

[gturn]

I typically shock with dichlor but the other night I used MPS. My TC level was around .5 ppm before I shocked. I used the MPS that came with my HS starter kit. I believe it's buffered since they recommend using 3 TBS per 250 Gallons. My spa is 450 Gallons so I used 5 TBS. I also added 1 TBS of dichlor to get some sanitizing power.

Anyway, tonight I checked my FC and it was around .5 ppm and my TC reading was 3 ppm. My water smells fine and believe the MPS did it's job. I've used MPS a few other times and had the same problem. I used a K-2005 Taylor test kit. Is it possible for MPS to give you a false TC reading?

How is your ph, if ph is low, clorine uses itself up, if it is to high it isn't as effective.  If the ph is off you just add to your total chemical count without getting much sanatizing. Clorine is very ph level sensative.

[Gomboman]

My PH is 7.4 I'm trying to figure out how my combined chorine reading went from .5 ppm  to 2.5 ppm after shocking with MPS. Must be a test error.  

[Vinny]

Gombo,

MPS plays havoc with the CC reading.  You probably don't have any CC and it's giving you a false reading.

Wait a day or two and then take the reading. Also, If you don't smell chlorine - it's a good indication that your CC is very low or non existant.

[Gomboman]

Thanks Vinny. I'm curious what type of MPS you are using? Also, how much do you typically use for shocking? Five to six tablespoons of the buffered type seems like a lot of product to dump in the spa.

[Vinny]

I have used Sea Klear MPS from Doc but I found a LARGE bucket in the garage from Leslies pools and that is straight MPS too. I'll go back to Sea Klear when I eventually use up this bucket. I originally bought the MPS for shocking the pool then found out it may (or does) cause high phosphates which will make algea grow, spas shouldn't have that problem.

As for how much, I use about 2 oz. Straight MPS seems to be used at 1 oz per 250 gallons and my tub is 400 gallons.

Using MPS is using a lot of product, shocking a tub to 10 PPM dichlor for me is 6 teaspoons and I usually don't shock to that level. Every 2 tablespoons is 1 oz; 6 teaspoons are 1 oz.

[gores95]

Silly question guys from someone who hasn't even had his spa delivered (next week).  Why shock with MPS rather than Dichlor?  I understand MPS does not kill bacteria and some even use MPS AND Dichlor to shock.  Any reason not to just use extra Dichlor?

BTW I plan on using a silver cartridge (Monarch or Nature 2) as well.

Thanks,

Marc

[Vinny]

Shocking with MPS allows you to use the tub quickly. It also does eliminate the crud that causes foaming. I have witnessed the foam disinergrate in 20 minutes after adding MPS.

If it's been a while since I added dichlor, I'll add dichlor after a 20 minute cycle of MPS.

[anne]

Gombo, I'm really glad you asked that question, b/c the other day I had the exact same issue: I suddenly seemed to have more CC after shocking with MPS.

Does anyone know at what level CC tends to be detectable by smell? I'm sure that some of us have better noses than others, but in general are we talking 0.1 or 1 or 3? I have yet to smell that from my tub.

[gturn]

Silly question guys from someone who hasn't even had his spa delivered (next week).  Why shock with MPS rather than Dichlor?  I understand MPS does not kill bacteria and some even use MPS AND Dichlor to shock.  Any reason not to just use extra Dichlor?

BTW I plan on using a silver cartridge (Monarch or Nature 2) as well.

Thanks,

Marc

By the time you add enough Clorine to do a shock your sanitizer levels will be to high to use the tub, sometimes for days.  I use Bromine and can still shock with Clorine, but I usually use the Non-Clorine shock (MPS).  A clorine shock raises the Bromine level quickly, because it chemicaly converts to Bromine, when using clorine as your sanatizer it raises the Free Clorine levels.  

Shocking is to raise the Oxidizer level, you need to shock to burn off the oils, lotions, and other gunk the sanatizer doesn't get at the lower sanatizer levels.  Using Clorine as a shock raises the oxidizer levels high enough to burn off that gunk but also raises the sanatizer level. A Non-Clorine shock raises the Oxidizer level and burns off the gunk but doesn't also raise the sanatizer levels as high.

[Dr. Spa™ Ret.]

What timing...... I was just reading two articles on this very subject;

http://www.poolspa.com/publications/sin/stories/shocktrt.htm

http://www.poolspa.com/publications/sin/stories/oxshock.htm

[anne]

Doc- those were great articles. I'm left with at least one thing that I dont think I understand- can anyone help? From the first article:

"First, the addition of chlorine to a pool containing ammonia (1) results in a growing production of combined chlorine (2). Once enough chlorine has been added to oxidize all of the ammonia, the combined chlorine rapidly breaks down (3). At this time, little, if any, chlorine remains in the water, because it has all broken down into nitrogen and chloride (4). Any chlorine added after this point will form free chlorine (5), because there is no ammonia to react with the chlorine now being added."

So shocking with chlorine breaks down chloramines, resulting in free nitrogen and chloride- so all the nasties are gone, there is no free chlorine left afterwards to sanitize? So if you add enough to make it to breakpoint chlorination "plus a little" you save sanitation as well?

From the second article:
"...using a non-chlorine shock can help to prolong the sanitizer residual, .....The shock treatment accomplishes this by oxidizing wastes and thus "freeing up" the chlorine or bromine to do its job as a disinfectant. Potassium monopersulfate does not, however, kill bacteria and cannot replace your choice of sanitizer"

So if I shock with MPS, in the presence of chloramines, I am also in a sense "sanitizing" since the MPS frees up chlorine already in the water back to it's free state, right? In this case, unlike with the chlorine shock that oxidized chlorine to chlorides, I am re-introducing free chlorine then.

And lastly.....gturn said "A clorine shock raises the Bromine level quickly, because it chemicaly converts to Bromine, when using clorine as your sanatizer it raises the Free Clorine levels."
I think I'm misunderstanding something, because chlorine cannot turn into bromine.....isn't it that chlorine present with bromides helps somehow to convert the bromine to its sanitizing form?

[Dr. Spa™ Ret.]

I'll go with your second, or middle question. Chlorine does 2 things. It oxidizes dead organic matter in the water, and it sanitizes. Generally speaking, chlorine will need to oxidize everything in the water before it will begin sanitizing. sooooooooooo, if something else does the oxidizing (MPS), that leaves more chlorine to sanitize.

[gturn]

And lastly.....gturn said "A clorine shock raises the Bromine level quickly, because it chemicaly converts to Bromine, when using clorine as your sanatizer it raises the Free Clorine levels."
I think I'm misunderstanding something, because chlorine cannot turn into bromine.....isn't it that chlorine present with bromides helps somehow to convert the bromine to its sanitizing form?

I think I confused you by including both Clorine and Bromine reactions in the same sentance.  Bromine sanatized water reacts differently than Clorine sanatized water when you add Clorine to the water.  A Bromine method has a Bromite base and the Clorine has a chemical reaction on the Bromite to form Bromine.  Bromine tablets contain both Bromine and Clorine, the bromine adds more sanatizer and the Clorine converts the bromite in the water into Bromine.  When Bromine destroys toxins it is changed into Bromite which can be converted back in to Bromine with a Non-Clorine shock or with Clorine.  Clorine will not turn into Bromine if there is no Bromite present which is the case when using Clorine as your sanatizer.
For more info on Bromine see this link:

http://www.askalanaquestion.com/bromine_for_spas.htm

[Gomboman]

Thanks Doc.

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When testing, you should be aware that while no interference will be detected when using OTO test kits, there is minimal interference with free chlorine readings on DPD tests. The DPD reacts with the potassium in the total chlorine test to give a false high combined chlorine reading, but there are test kits available to eliminate monopersulfate interference.