So I'm having a Halloween party in a few days and am planning on having guests bob for apples out of a tub. The tap water here has 1.5ppm FC. This doesn't seem like enough to kill germs fast enough to prevent them from spreading from guest to guest. What would be a safe FC that would kill germs within a reasonable amount of time and not give the guests a free facial chemical dermabrasion.

I realize this is a little out of the realm of the typical sized body of water discussed here. I'm hoping someone might have an idea.

I'm not sure, but I am willing to guess that this is a question that has never before been asked on our forum.

Given that you have zero CYA and the short time in the tub, 1.5 ppm FC is plenty to kill anything that might get introduced. You could add a few tablespoons of bleach to the tub if you're doing it in the middle of the day out in the sun, but otherwise I wouldn't worry about it.

What Hp pump and what size filter on this apple tub? Sand, cartridge or DE?

One method used by homebrewers to sanitize their equipment is to mix 1 oz. of bleach with 5 gal of water, then add in 1 oz. of white vinegar.

I've done it before, but I can't speak to the chemistry, or the taste. Something to think about.

Just a guess, but I imagine your guests will be "bobbing" with only their faces submerged. (At least, I certainly hope so)

I don't think you have quite the exposure to germs, etc. that might be found in a pool.

Tap water is likely perfectly sufficient but a tablespoon or so of bleach might give you more reassurance and would be undetectable if you put it in a few hours before.
Party on, masqueraders!

If you use your whole body I think it's technically "Roberting" for apples.

Replace the water with Listerine! Fresh Breath for everyone!

I suppose I could hook up the Hayward pump and sand filter to the tub. That will change out the full 20 gallons every minute. I just hope no one's hair gets sucked into the intake.

Seriously though, I think I just add a teaspoon at a time until I get to around 5ppm. Isn't the upper limit allowed in public pools, 7ppm?

It's actually double birthday and Halloween themed party with about 40-60 3rd graders. The fear is everyone getting sick from one person. It's amazing how anal parents are these days. No one would have even worried about this when I was a kid. I just want to be able to kill anything in about 30-60 seconds.

Does anyone know if the PoolCalculator is accurate down at 10-20 gallons? Jason?

yes it is.

Note that the chlorine is going to get used up faster than you'd think because of the apples in the tub, let alone the saliva and skin oils from the bobbers. As was noted by others, the risk will not be from fecal bacteria, but mostly from viruses and/or bacteria in saliva and mucous. Just maintain 1 ppm FC minimum at all times, so you'll have to monitor periodically and probably overshoot quite a bit to handle the chlorine demand. For such short exposures, having the chlorine level far higher should not be a problem. If you want to slow down the chlorine loss rate, but also slow down the kill times, then you could use Dichlor or granulated Trichlor. That way, you won't have to be monitoring the water as often as the chlorine will last longer while still providing 99.9% kill times in the 1 minute range. Then again, if you want the very fastest kill times, then just add chlorine bleach every now and then as needed.

On the other hand, this isn't really that much different than a classroom of little kids playing together at school where it's very common for one kid to infect a whole bunch of others with some virus.

Don't bet on it!

Or, at the very least, don't let the dog play. If they stick their snouts in the tub . . . well, do you know where that tongue has been?

In all seriousness, are there really parents who worry about germs when bobbing for apples? Their kids live in a bubble? Sheesh!