Wait time between chlorine readings?

[Onlyhottub]

We've had our Hot Spot Tempo almost 2 weeks and noticed that the water is getting very cloudy. We've been using it pretty heavily, and each time we test it, the chlorine level is too low, so we add more. I think we've shocked it at least 4 times, but haven't seen the chlorine level rise much. Our plan is to shock it a few times this weekend and wait to go back in until the chlorine level is in the OK range. I have a few questions...how soon after we add chlorine can we get an accurate reading when we test the water again? Also, we've been shocking it with 4 tsp of dichlor...is that not enough (the tub holds 400 gallons)? On average, we have 3 people who use the hot tub for about 1/2 hour to an hour a day (I'm sure our usage will go down eventually once the novelty wears off). Thanks for any help you can provide!

[hottubdan]

Sounds like you have heavy demand with your new spa.  Double up.  You might want to clean filter also.

[chem geek]

Do you have an ozonator?  Without an ozonator, the rough rule-of-thumb is that every person-hour of soaking in a hot (104ºF) tub requires 3-1/2 teaspoons of Dichlor or 5 fluid ounces of 6% bleach (3-1/2 fluid ounces of 8.25% bleach) or 7 teaspoons of non-chlorine shock (43% MPS) to oxidize bather waste.

Your 3 people for 30 minutes to an hour would be 1.5 to 3 person-hours so would need 5 to 10-1/2 teaspoons of Dichlor so the 4 teaspoons you've been adding hasn't been enough.  However, with an ozonator and regular spa usage, the needed amounts are usually about half that of the rule-of-thumb.

Also note that a new spa has higher oxidizer demand initially and usually you want to do a decontamination during your first fill of water to remove grease and biofilms using a product such as SeaKlear Spa System Flush or Ahh-Some.