How much non-chlorine shock (MPS) for your hot tub

A routine dose of 45% non-chlorine shock in a chlorine tub is 1.5 oz per 200 gallons: 3 oz (85 g) for a 400 gallon tub. Use it weekly and after heavy soaks. In a bromine tub the calculator sizes a smaller dose from your bromine reading, because the full label dose can read about 27 ppm bromine.

MPS shock calculator

Add

3oz

of Non-chlorine shock (MPS 45%)

85 gabout 4 tbsp by volume

The routine label dose for 400 gal: once a week, and after a heavy soak.

Side effects: TA −12 ppm.
MPS reads as combined chlorine on DPD tests for about a day. Test CC the next morning.
Run the jets with the lid open and wait at least 15 minutes (20 after pH decreaser) before anyone gets in.
MPS shows up as combined chlorine on DPD tests for about a day.
MPS burns off what soakers leave behind but does not sanitize. Keep chlorine in range as well.
Leave the cover open for at least 15 minutes with the jets running.

Check the product label. Strengths vary by brand, so enter the % printed on yours. Add one chemical at a time, into the water, and never mix chemicals.

Save this test and get a reminder before your next soak.

Spa Calc for iPhoneComing soon to the App Store

What MPS does

Potassium monopersulfate (MPS) oxidizes the waste soakers leave behind without adding chlorine, so you can usually soak again soon after. It is not a sanitizer: keep chlorine or bromine in range too. In bromine tubs it reactivates the bromide reserve, which raises bromine: test before soaking.

Testing after MPS

MPS reads as combined chlorine on DPD tests for about a day. Test combined chlorine the next morning, or use a test with an MPS neutralizer.

Questions

Is non-chlorine shock safe for inflatable hot tubs?

Yes, at the label dose. Leave the cover open for 15 minutes afterwards.