There will be, or should be, chemicals in the water, so this will pretty much certainly kill any plants in said yard. Drain it to a gutter or stormwater outlet instead.
If we can get the measurements of the garage and the depth of the pool, we can work out now much that water will weigh.
[quote=“Askance, post:21, topic:583903”]
There will be, or should be, chemicals in the water, so this will pretty much certainly kill any plants in said yard. Drain it to a gutter or stormwater outlet instead.
QUOTE]
Won’t be chemicals if she’s pulling hot water from her hot water tank, and very few chemicals if she’s pulling water from a hose (regardless of source - the chemicals are in the hose) but as people water their plants with hoses all the time and plants don’t die in spades, I think they’ll be ok there. The real problem is if you flood the water all out into one place, you could wash out the topsoil in an area and cause little miniature canyons that are hard to get rid of.
As for the “should be” - trying to measure out salt or chlorine ratios for an eensy tiny wading pool that’s going to be used for a few hours by grown people inside? So not worth it, and potentially dangerous if you mismeasure the chemicals.
I don’t think any of their 30ish year old friends are going to pee in the wading pool in their living room. 
Did you add chemicals to your kids’ wading pools when you filled them for an afternoon?
Sounds awesome!
Also about using warm water, you may be able to connect a hose directly to your hot water tank (heater). But the amount of hot water you can get out of them continuously is going to be very low, you will not want to run . If you have a instant hot water system it would work better. Also try to cover the pool up while filling as it will take a long time to fill with hot water and you can lose much heat during that time.
Good luck
So it’s settled then. Pool party at miss elizabeth’s place! Woooooo!!!
Don’t worry…the chances of this one ending with an MX missile sprouting out of the basement are pretty low.
For an 8’ diameter pool with 30" of water in it? What calculation are you using?
I have one of those pools and have a few suggestions for you.
I assume there will be drinking? To make entry and exit from the pool simpler for the imbibers I recommend what I do. Get some concrete blocks and stack a simple two step entry. This does a couple of things, makes getting in, easier for everyone and keeps people entering and exiting from one location. Accidents to the walls are most likely to occur with people getting in and out willy nilly and not paying much attention to others doing likewise. It’s watery plastic after all, one slip or bump into each other and down they go with the pool wall, yikes!
When I have drinkers over, I add a second, simpler, single block, on the inside of the pool (covered with an old towel to not abrade the pool). Decreasing the chance of slipping on entry.
Also I would consider only plastic cups for drinks. Skip the floating candles, and avoid pool toys that will get thrown around - someone is sure to dive for it and take out the pool wall. I’d go with kids toys from the dollar store, wind them up and they swim, water pistols, kiddie buckets etc. While you’re there consider some cheap beach towels, good to decorate and sure to come in handy, (especially if you have major spillage!), and you won’t care should they get destroyed!
You might consider some sand too, it’s good for the bottom of the pool, just a dusting. Yeah, I know, long run not a great idea, but one night won’t hurt and will help keep people from slipping.
Also I always use a kitty litter shaped pan, filled with water at the entry steps, for people to step in before entering the pool, it just keeps lots of crap out of the pool, especially in the yard where there is grass and dirt.
Also you won’t have to siphon the water out, there is a drain on the side and it come with an adapter for a garden hose!
Sounds like an awesome party, do take some pictures for us, or, at least update us on how it went!
Most public pools (like the one at the Y) have a temperature around 84 degrees. (At least, that’s what my Y’s pool whiteboard almost always said). So shoot for something around there - use a thermometer to judge the water temp.
I have slept on a water bed that we filled that day with water from the tap. 'Bout froze to death - it was cold. I like your idea of augmenting with warm water or even large pots of boiled water to get the temperature comfortable.
Perhaps getting a very long hose and running it outside in direct sun, possible on the rooftop could be a better alternative then using your hot water supply.
You mentioned lights in the room - nothing that would fall into the pool I hope?
Water weighs about 8.34 pounds per gallon The Weight of Water so for that pool in **miss elizabeth’s **link that holds 650 gallons the weight would be 5421 lbs.
A large car weighs about 4000 pounds http://answers.askkids.com/How_Stuff_Works/how_much_does_a_car_weight
Since the pool won’t be there very long and the weight will be spread out over the surface area of the pool I don’t think it would crack or damage the slab, but maybe it will help make your decision once you see the numbers involved.
Wouldn’t work, the water in the hose would get warm, but the few gallons of warm water would just get kablooshed out by the cold stuff once the tap was turned on. It might work if the hose was out in the sun and just left on a slow trickle, but for 650 gallons he’d be celebrating his 99th birthday 
Had friends who had a pool in their house once. Mildew everywhere. I think it was more the hot tub, but it really changed the environment in the room.
How high is the ceiling in that room? I’ve got a pool like that, and the way in & out is via a 2 sided ladder - so at some point, your head is a good 9-10 ft above the ground.
Make sure you measure your hose flow rate, so you know how early to start filling. And unless you’ve got a gigantic water heater, don’t even bother trying to heat it up that way - if your tap water is 55F, and the water heater provides 140F water, the 60 gallons or so you’ll get will only increase the temp of a 650 gallon pool to 63F
After only one night?
Damage from a catastrophic spill might be excluded from your homeowner’s coverage as flood-related.
Gross: Swimming in untreated anal/orifice juices of others.
You need filtration and sanitizers.
If you can verify the garage floor is a concrete slab exceeding 4" in depth, laying on a bed of sand, I think you can get away with it. The weight load would be much more distributed that the near point loads of 4 tires.
Take that with a large amount of salt. I’m a controls engineer, not structural.
ETA: when I was a fireman, we’d set up our 3000 gallon drop tanks just about anywhere we had to to fight a fire, and I don’t recall any soil or pavement that could not support it. It was 20’X20’X3’, wouldn’t want to swim in it, however.
It’s one day - she’s going to fill it in the morning, have the party, then drain it. Filters & sanitizers won’t make a difference.
And they won’t be swimming - the listed pool is 30" deep, which will only be filled about halfway with water.
Go for it! I used a pool in my house for childbirth. If you have a tankless hot water heater you’re golden. If you have a tank, set it the hottest you can, and get an RV hose to convey that water from the laundry hookup. You can add cool water directly from the outside garden hose through a window.
The hardest part is getting ALL the water out of the pool in order to get the thing back out of your house. Also know that you will have water everywhere from wet guests getting drinks, walking to the bathroom, etc.