My Shocking Problem!

[bart6453]

I have a quick question about shocking....

I recently switched from di-chlor to Bleach to sanitize my tub. Everything is fine and well, but after I shock with Bleach to 15PPM FC, how long should it take a 400 gallon tub to get down to 4PPM FC??

Also, is it better to use bleach or MPS??? I quit using MPS because it made my combined chlorine test scale off the chart.

[Nitro]

Depends on your Chlorine Demand?

[bart6453]

Depends on your Chlorine Demand?

Ok....I guess I was thinking that there was a magical point at which chlorine reacted with itself and burnt off faster. But is it just CC that burns off when you get the FC high enough???

If that is the case, my chlorine demand is somewhere around 30%....

[PaulR]

If it's outdoors, you could leave the cover off and let the sun burn some off for you. Otherwise you just wait it out.

--paulr

[bart6453]

If it's outdoors, you could leave the cover off and let the sun burn some off for you. Otherwise you just wait it out.

--paulr

great..that's pretty much what I was thinking.

So out of curiosity, why would a guy use MPS as a shock???? unless you wanted to get in quickly after you shock, or you wanted to increase the rate at which your CC is oxidized during a soak.

thanks for the input!!!

[bdwoods]

If it's outdoors, you could leave the cover off and let the sun burn some off for you. Otherwise you just wait it out.

--paulr

great..that's pretty much what I was thinking.

So out of curiosity, why would a guy use MPS as a shock???? unless you wanted to get in quickly after you shock, or you wanted to increase the rate at which your CC is oxidized during a soak.

thanks for the input!!!

I found that the MPS totally whacked my balance out. I did it 2 weeks ago and my PH is still drifting after been spot on for a month. It has a very low PH.

I'm also using an N2 stick now, which recommends MPS shock but I'm hesitant to put the stuff in my tub.

In my Taylor kit it says to multiply the CC number by 10 and shock with chlorine to that number - is this the case? It says if you don't, chlorine won't get rid of CC and will actually increase it. This seems like a lot - and enough bleach to whack out your PH as much as the MPS!

I understand why someone would find this confusing.

[tony]

great..that's pretty much what I was thinking.

So out of curiosity, why would a guy use MPS as a shock???? unless you wanted to get in quickly after you shock, or you wanted to increase the rate at which your CC is oxidized during a soak.

thanks for the input!!!

I like to use MPS to shock. As a daily user I don't like to wait for my free chlorine level to drop. I use bleach to chlorinate on a daily basis, so the low pH of non buffered MPS tends to keep my water in balance. For instance, since my water change in early April, I have yet to need any acid to lower my pH. This is without the use of borates or any pH balancing product. I shock weekly, though because I add chlorine daily, I most likely don't need to shock at all. MPS is also more fool proof. If you add too little, it oxidizes what it can...if you add too much, it waits for something to oxidize. With a chlorine shock, if you don't add enough to reach breakpoint chlorination...you have not shocked the spa. IMO, MPS works well.

[bart6453]

great..that's pretty much what I was thinking.

So out of curiosity, why would a guy use MPS as a shock???? unless you wanted to get in quickly after you shock, or you wanted to increase the rate at which your CC is oxidized during a soak.

thanks for the input!!!

I like to use MPS to shock. As a daily user I don't like to wait for my free chlorine level to drop. I use bleach to chlorinate on a daily basis, so the low pH of non buffered MPS tends to keep my water in balance. For instance, since my water change in early April, I have yet to need any acid to lower my pH. This is without the use of borates or any pH balancing product. I shock weekly, though because I add chlorine daily, I most likely don't need to shock at all. MPS is also more fool proof. If you add too little, it oxidizes what it can...if you add too much, it waits for something to oxidize. With a chlorine shock, if you don't add enough to reach breakpoint chlorination...you have not shocked the spa. IMO, MPS works well.

ah...more good information....thanks!

[bdwoods]

great..that's pretty much what I was thinking.

So out of curiosity, why would a guy use MPS as a shock???? unless you wanted to get in quickly after you shock, or you wanted to increase the rate at which your CC is oxidized during a soak.

thanks for the input!!!

I like to use MPS to shock. As a daily user I don't like to wait for my free chlorine level to drop. I use bleach to chlorinate on a daily basis, so the low pH of non buffered MPS tends to keep my water in balance. For instance, since my water change in early April, I have yet to need any acid to lower my pH. This is without the use of borates or any pH balancing product. I shock weekly, though because I add chlorine daily, I most likely don't need to shock at all. MPS is also more fool proof. If you add too little, it oxidizes what it can...if you add too much, it waits for something to oxidize. With a chlorine shock, if you don't add enough to reach breakpoint chlorination...you have not shocked the spa. IMO, MPS works well.

Maybe the brand of MPS I grabbed has a lower PH than most, because it really screwed my PH and TA, and I use chlorine everyday. Perhaps when using MPS you need to have a higher TA?

I loved what it did for my tub, it was truly "shocked" and very clean but just caused my PH to keep dropping to 7.2 for about 3 days - everytime I'd add acid, it would drop again!

I may just learn how much it lowers the TA and PH, and then bring it back up immediately and hope that it returns to balance.

[tony]

great..that's pretty much what I was thinking.

So out of curiosity, why would a guy use MPS as a shock???? unless you wanted to get in quickly after you shock, or you wanted to increase the rate at which your CC is oxidized during a soak.

thanks for the input!!!

I like to use MPS to shock. As a daily user I don't like to wait for my free chlorine level to drop. I use bleach to chlorinate on a daily basis, so the low pH of non buffered MPS tends to keep my water in balance. For instance, since my water change in early April, I have yet to need any acid to lower my pH. This is without the use of borates or any pH balancing product. I shock weekly, though because I add chlorine daily, I most likely don't need to shock at all. MPS is also more fool proof. If you add too little, it oxidizes what it can...if you add too much, it waits for something to oxidize. With a chlorine shock, if you don't add enough to reach breakpoint chlorination...you have not shocked the spa. IMO, MPS works well.

Maybe the brand of MPS I grabbed has a lower PH than most, because it really screwed my PH and TA, and I use chlorine everyday. Perhaps when using MPS you need to have a higher TA?

I loved what it did for my tub, it was truly "shocked" and very clean but just caused my PH to keep dropping to 7.2 for about 3 days - everytime I'd add acid, it would drop again!

I may just learn how much it lowers the TA and PH, and then bring it back up immediately and hope that it returns to balance.

If you use dichlor and shock with non buffered MPS, it will drop your pH and thus your TA. Dichlor is slightly acidic and MPS is very acidic, so this would naturally bring your pH down. A higher TA would help with this. I use bleach daily which has a high pH, so the low pH of MPS helps keep me in balance. If you use dichlor and want to shock with MPS, you may be better off with a buffered version such as Leisure Time Renew which is pH neutral.

I don't want to discourage others from shocking with chlorine. I was just replying to the question "why would one want to use MPS." Shocking with chlorine has the benefit of a true "super chlorination." I just like MPS for weekly maintenance. When I have a water problem, though, I shock with chlorine.

[Jim F]

After shocking with MPS after a hot tub party, I noticed that the next day, the TA reading (using Taylor kit) was "off the chart", meaning when I added the green drops, the water sample changed to red not green. (pH had dropped to 7.1 from 7.5)

I know MPS gives false FC and CC readings

Does it also make TA readings unreliable? If so, for how long?

[DonR6702]

After shocking with MPS after a hot tub party, I noticed that the next day, the TA reading (using Taylor kit) was "off the chart", meaning when I added the green drops, the water sample changed to red not green. (pH had dropped to 7.1 from 7.5)

I know MPS gives false FC and CC readings

Does it also make TA readings unreliable? If so, for how long?

No, it shouldn't make the TA reading unreliable - but it does lower TA as well as pH. Alkalinity and pH go hand-in-hand. Anything that lowers the pH will lower the alkalinity too, and vice versa. There's no need to wait around for things to correct themselves because they probably won't. If you're using non-buffered MPS, add TA increaser (sodium bicarbonate, or baking soda) to get the alkalinity back up, and your pH will come up to. I use non-buffered MPS and practically never need to add anything to raise the pH, only the alkalinity.

[Nitro]

Keep in mind, pH will rise naturaly from aeration. Your TA is what you need to watch, and adjust. Think of TA as your thermostat, and pH as the temperature. Adjust TA up, or down to keep pH in line.