If you don't have stabilizer in the pool (aka CYA), the sun is going to burn off the chlorine about as fast as the trichlor puck can put it in. With zero stabilizer, you need to be keeping 1-3 ppm of chlorine in the pool at all times. If you can tell me the volume of your pool in gallons or the dimensions (do you mean 18 foot diameter round pool, 48 inches deep? Or do you mean 18 feet wide, 48 feet long, and how deep?) then I can tell you how much plain, unscented bleach you need to get in the pool for it to be safe to swim in today. (48ft x 18 ft is a huge pool for ABG, but you're expecting 20 people, so maybe it's reasonable?).

If the pool is clear, and you can get the bleach in the pool, then it's okay to swim for tonight. You'll need to add more chlorine after the people get out, though, because "people goo" is liable to use up what you put in there to begin with. Here's where you need something other than strips, which aren't reliable--go to WalMart and see if they have the hth 6-way drop kit, or if they don't, then at least get the cheapie OTO kit (uses red and yellow drops for pH and chlorine). You can use that to measure chlorine for now and at least keep the pool safe until you get the water balanced and some CYA in it. After the sun is off the pool, and the swimmers are out, measure your chlorine again, and add enough to get back up over 3 ppm (again, if you'll tell me pool volume, I can help you with amounts). You'll need to do the same a few times during the day, at least until you get some CYA in the pool.

If your pH is high, and CYA is low, then using dichlor for chlorination is ideal for your pool. If you have a Sam's nearby, look for the PoolBrand dichlor chlorine (it's a powder). If not, Amazon carries a Kemtek dichlor that is also good. Don't buy dichlor from other sources, because a lot of them recently have changed formulas and are adding "goop" to it that makes it react unpredictably in pools. I would use the dichlor in your pool until your CYA gets to around 40-50 ppm, then switch to plain bleach for chlorination.

In the meantime, log out of the forum, go to the main forum page, under the second section of the forum--the first set of threads is called "Pool chemistry for Intex pools", and once you open that, the second sticky is called "super simple pool chemistry recipe......". Read through that, and it should help you understand better what you're doing. if you have further questions, feel free to come back and post them here.

Welcome to the forum!