Jump to content

How Long Does Mps Reside In Tub?


spawn

Recommended Posts

In Nitro's Dichlor-Bleach method, he suggests that MPS may be used before or during a party to oxidize waste so that FC remains available in the tub. Perhaps a stupid question but what happens to excess MPS after all waste has been oxidized?

It dissipates, leaving dissolved solids (which anything you add to the hot tub leaves dissolved solids)

Link to comment
Share on other sites

Yup, when chlorine gets used up it results in sodium chloride salt (when accounting for any needed pH adjustments). When MPS gets used up, it results in potassium sulfate salt.

Note that some people get a reaction (skin irritation) from the minor contaminant (potassium persulfate aka potassium peroxydisulfate) that comes with MPS (potassium monopersulfate which is actually a triple salt with potassium sulfate and potassium bisulfate). This doesn't seem to happen when people use MPS with Nature2, probably because the silver ion decomposes this contaminant.

Link to comment
Share on other sites

Thanks Hillbilly Hot Tub and Chem Geek. I have heard that after adding MPS it is okay to enter the tub after waiting 15 - 30 minutes. So after 30 minutes would one expect that there would be no "active" MPS in the tub or any negative aspects?

The rate of dissipation of the MPS will depend on the oxidizer demand. If there are a lot of organics to oxidize, then the MPS will be consumed fairly quickly at hot tub temperatures. If there are not a lot of organics to oxidize, then the MPS should last longer (perhaps 24 hours).

I think that you would be OK as long as you limited the amount of MPS to 1 ounce weight per 500 gallons of water and waited 1 hour before going in. I think it is better to add the MPS after soaking and based on chem geek's rule of 7 teaspoons per person hour.

Link to comment
Share on other sites

The rule to wait a short time is based on ensuring good mixing of the MPS throughout the water. It's not intended to have the MPS go away completely. As QCD noted, how long this takes depends on how much there is to oxidize (and on how quickly it gets oxidized). Some systems, such as Nature2 with MPS, instruct the user to maintain an MPS level at all times since it (along with silver ion) is the primary sanitizer. You soak with MPS levels high if you follow these instructions. It's like swimming with chlorine in the water -- at recommended levels it's safe, though it is an oxidizer so will oxidize skin, hair, swimsuits, etc.

Link to comment
Share on other sites

Thanks Hillbilly Hot Tub and Chem Geek. I have heard that after adding MPS it is okay to enter the tub after waiting 15 - 30 minutes. So after 30 minutes would one expect that there would be no "active" MPS in the tub or any negative aspects?

this is true in a chlorine system but not in a bromine system where MPS oxidizes the bromide reserve in the water into hyopbromous acid (bromine sanitizer). MPS cannot oxidize chloride into hypochlorous acid in a chlorine system.

Link to comment
Share on other sites

Thanks all. I have been trying to figure out whether and how to use MPS in my tub. I have been considering it for a couple of reasons. FYI, I use the dichlor bleach method.

My tap water is 7.8 pH and with TA of 30 so when I do a fill I increase TA to 80, adjust Ch (increasing from 30 to about 170) and then use dry acid to get pH back down to 7.5. On my recent fill I added Gentle Spa to see how I like it and especially to see if it helps mangage my pH.

I know I don't need to get pH down to 7.5 to start but I have decided to because my pH tends to rise. Probably the main reason for this is the way we use the tub. My wife and I get in almost every night for half an hour and we turn the jets and air on high. We sit in front of the jets part of the time but we also enjoy just sitting in the water, not in front of the jets but having the water active and moving whirlpool style - we like it better with jets on high than jets off or on low. In our round D1 Arena there are just about as many places to sit with no jets as with jets and at different levels and it works great for us. So each day we are running the jets on high and aerating the tub for half and hour, which I understand will raise pH. Up to now I have managed this by adding dry acid every couple of weeks.

I am considering doing an occassional shock with MPS. I understand that it is not necessary to shock if you don't have much CC and have adequate FC but some advise doing a weekly shock as a preventative measure. Before my recent fill I found I had CC of about 2.0 although I had adequate FC readings so I have been wondering if the precautionary MPS shock might not be a bad idea. The fact that the acidity might somewhat help my slowing climibing pH is also part of my reasoning.

This lead to my question about any downside to adding MPS if you don't really have much CC in the tub. I know I can shock with bleach and may not need to shock at all. In general, my water is great (except for recently before my dump and fill). Any thoughts or should I just keep doing what I'm doing? Thanks again!

Link to comment
Share on other sites

Also, do not raise the TA to 80 ppm. Just get it to 50 ppm and leave it there. The higher the TA level, the more the spa is over-carbonated which will result in faster carbon dioxide outgassing which causes the pH to rise. This chart shows how over-carbonated water is at various TA and pH levels. At a pH of 7.5 with a TA of 80 ppm, there is 7 times more carbon dioxide in the water as there would be if in equilibrium with the air. At a TA of 50 ppm and pH of 7.7, it's only 1.8 times so targeting a TA of 50 ppm and letting the pH settle in near 7.7 should lead to substantially slower pH rise and less acid needed to compensate.

Link to comment
Share on other sites

  • 8 years later...
On 11/18/2010 at 7:24 PM, quantumchromodynamics said:

The rate of dissipation of the MPS will depend on the oxidizer demand. If there are a lot of organics to oxidize, then the MPS will be consumed fairly quickly at hot tub temperatures. If there are not a lot of organics to oxidize, then the MPS should last longer (perhaps 24 hours).

I think that you would be OK as long as you limited the amount of MPS to 1 ounce weight per 500 gallons of water and waited 1 hour before going in. I think it is better to add the MPS after soaking and based on chem geek's rule of 7 teaspoons per person hour.

Is MPS guaranteed to dissipate within 24hrs?  I'd like to get a reliable reading for the Total Chlorine from a Taylor test kit (K-1004, PPMS interferes with the Total Chlorine reading).  Trying to avoid having to buy the expensive K-2041.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Unfortunately, your content contains terms that we do not allow. Please edit your content to remove the highlighted words below.
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...