MPS for 400 gallons
| Dose | Grams | Ounces | Approx. measure |
|---|---|---|---|
| Weekly | 85 g | 3 oz | 4 tbsp |
| Two doses | 170 g | 6 oz | ½ cup |
| Three doses | 255 g | 9 oz | ¾ cup |
How much non-chlorine shock for a 400 gallon hot tub
A 400 gallon hot tub takes 3 oz (85 g) of 45% non-chlorine shock per dose, about 4 tbsp. Use it weekly and after heavy soaks. Many labels allow soaking about 15 minutes later. In a bromine tub, test bromine first: this full dose can read about 27 ppm from the bromide reserve, so the calculator sizes a smaller routine dose from your reading.
Run it with your numbers
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 StoreAbout non-chlorine shock
MPS oxidizes the sweat, oils and lotions soakers leave behind, without adding chlorine. It does not sanitize, so keep chlorine or bromine in range too. In a bromine tub it also reactivates the bromide reserve.
MPS shows up as combined chlorine on DPD tests for about a day, so test combined chlorine the next morning. It slowly lowers alkalinity: check TA every week or two.
A 400 gallon tub
400 gallons is a typical 6 to 7 person acrylic tub. Doses are larger but the water is steadier; still test before every soak, and drain about every 67 days with two soakers a day.
Questions
How much non-chlorine shock for a 400 gallon hot tub?
3 oz (85 g) of 45% MPS per dose.
How long after non-chlorine shock can I use the hot tub?
Many labels allow about 15 minutes with the jets running. Follow your product’s label and test sanitizer first. In a bromine tub, soak only once bromine reads 6 ppm or less.
Does MPS replace chlorine?
No. It oxidizes waste but does not sanitize. Keep free chlorine at 3 to 5 ppm or bromine at 4 to 6 ppm.