A Shocking Question

[rckymtntim]

Hi All,

I'm using Nitro's bleach method. I have a Marquis Spirit 165 gal. My current numbers are:

FC= 6.6

CC=0.2, I'll check my numbers again this afternoon

PH 7.7

TA=60

TH=170

CYA=35

CD about %35

Temp=102

using ozone and N2

I am only using bleach at this point. I don't like using MPS as it gives me a rash. We usually use the tub 2-3 times a week 2 people for about an hour. After each use I add 1/2 cup bleach. Before leaving for work Monday mornings for 10 days I add 1 cup of bleach. My wife adds about 1/2 cup bleach every other day while I'm gone and 1/2 cup bleach if she uses the spa. The water is crystal clear and always ready when I get home.

My 2 question are, do I need to add anything else to shock the spa? If I put MPS in before I leave to shock will it dissipate before I get back after 10-11 days.

Thanks for the advice,

Tim

[chem geek]

Tim,

Your 35% chlorine demand (when not using the tub) is probably due to your ozonator so is expected. It's a bit surprising that the MPS irritates you since you have N2 and the silver ions from that should break down the most irritating component in MPS. Perhaps the actual MPS (monopersulfate) irritates your skin -- it is a reasonably strong oxidizer like chlorine.

2 people for an hour would normally be around 10 fluid ounces of 6% bleach if you didn't have an ozonator, so your 1/2 cup (4 fluid ounces) sounds like our ozonator is doing a good job and is consistent with the 40% of rule-of-thumb amount they found.

If you are consistently maintaining at least some chlorine residual level and measure 1-2 ppm FC before your soak, then you shouldn't need to shock -- possibly ever (except on refill with fresh water). As for using MPS, it should be gone after a few days, let alone 10-11 days, though it doesn't really dissipate (it doesn't outgas as chlorine can do a little). How quickly it gets used up depends on what there is in the spa to oxidize. Since you have an ozonator, there probably isn't a lot. Since you are sensitive to MPS, I don't see much point in using it at all.

Richard

[rckymtntim]

Thanks for the quick response. Sounds like I'm on the right track.