Question about test strips

[LStoner]

I bought some test strips to read the TC and FC. I'm using an N2 cartridge and put the recommended amount of chlorinated shock (2 tbsp. of SpaGuard Enhanced Shock) in to activate it. I have about a 300 gallon tub. It's been a few days now. The test strips arrived today. The TC and FC showed up zero. So, I added 1.25 oz. of MPS for the first time and let the tub run. I tested again after about an hour and still no FC registers, but an OK reading for TC. Will MPS not show up in the FC pad of the strip? Or do I also need MPS strips. I went ahead and ordered some just in case. I'm just not sure the proper way to read these strips so I know when I should add MPS and/or when I should add the regular chlorinated shock. Any thoughts? Thanks.

[Vanguard]

MPS is not chlorine.  It won't make chlorine show up by adding it.  It may equal out your TC and FC readings since the idea of shock is to get rid chloramines.  When FC does not equal TC, the difference is chloramines.  Those are what make your water smell bad, your eye burn, etc.  MPS burns out the chloramines, but does not add chlorine to the water.

To get your readings up, you'll need to add more chlorine.  Two teaspoons of chlorine will not last very long - even in 300 gallons.

[Gomboman]

When I add MPS it will give me false chlorine readings using my Taylor test kit. I'm assuming you are also getting false readings with your Test Strips. Perhaps someone can explain how this happens.

[Dr. Spa™ Ret.]

Test strips typically test the oxidation ability of the water. MPS test strips test for the oxidation ability and are calibrated to give a proper reading for MPS. Bromine test strips test for the oxidation ability and are calibrated to give a proper reading for Bromine. chlorine test strips test for the oxidation ability and are calibrated to give a proper reading for chlorine.

Bromine test strips test for the oxidation ability and are calibrated to give a PROPER reading for Bromine. MPS WILL cause a positive reading, BUT will be COMPLETELY INCORRECT.

[LStoner]

I wrote 2 Tbsp. of chlorine. Tbsp=tablespoons.

Anyway, everything I've researched says that MPS is supposed to take the place of chlorine shock so that my towels don't bleach out, etc. Also, everyone keeps saying that the eye burning and the chemical smell happens when I need to shock more. Sorry, but the only time I have a problem with those things is when I do put more shock in. Otherwise, no smell and crystal clear water. I kept putting more chlorine in according to suggestions with my last fill and guess what...I had to empty the tub and start over after a week and a half because it ruined my water. Not trying to sound rude here, I'm just frustrated.

So, again, if anybody has a formula of knowing when to put chlorine shock and/or non-chlorine shock in while using a combination of chlorine and MPS test strips, I would love to know. There's got to be somebody out there because I know I'm not the only one that uses MPS. It's just this is the first time using it for me so I don't know the tips and tricks on it.

[Hillbilly Hot Tub]

Spa Guard enhanced shock has chlorine and MPS in it (along with clarifier and PH stablizer) so you should be getting a reading on the chlorine test strip.

[LStoner]

For some reason, the first dosage of the fill didn't show anything after a couple of days. I added in non-chlorine shock and it showed a reading on TC. I understand that's a false reading. I decided to add some more enhanced shock in yesterday and today tested again. The TC was still higher than the FC and the FC still wasn't in the Okay range. So, I added just a little more enhanced shock.

So, am I understanding right that somehow the TC and FC should be the same or the FC should be more? I don't know how TC can ever be lower when it's the total chlorine. And if I'm using the non-chlorine shock in between using the chlorine shock, won't that make the TC read higher too (falsely)? Seems that would be the case after seeing what happened when I put it in before. That's why I ordered the MPS strips too. I thought that maybe there would be some way that I could use both test strips and subtract my MPS reading out of the TC to know what the true reading is. Is this true or was my thinking off?

Just trying to figure out when I should put in MPS and when I should put in the Enhanced Shock. On the plus side, my hot tub water is staying sparkly this time. I know it's only been 5 days, but that's longer than the last fill that was ruined after a week and a half.