OK,

First thing, you are not going to solve this in a day or in 2 days. But if you follow our instructions, you may well get your pool nice and clean in time for your party. Your PRIMARY ingredient is what we call POPP, which stands for Pool Owner Patience and Persistence.

As Polyvue said, we need "readings" from a new pool water test. Take it to the pool store and get them to give you the following:

1)Free Chlorine (FC)
2)Combined Chlorine or Chloramines (CC)
3)Total Chlorine (TC)
(if they give you FC and EITHER CC or TC, it's OK)
4) pH
5) Total Alkalinity (T/A) they may give you 2 numbers so report them both.
6) Stabilizer, aka CYA, aka Cyanuric Acid
7) Total or Calcium Hardness (CH)

They'll probably give you a phosphate level readout and tell you to buy phosphate remover. Don't waste your money, no matter HOW hard a sell they try.

Same with calcium. You have a vinyl pool. Calcium does NOTHING for a vinyl pool but cause trouble if you have too much. That will be another hard sell--to add calcium. Don't do it, no matter what they say.

Next: For now you are DONE buying things called "shock" and other pool store chemicals. The ONLY pool store chemical is Liquid chlorine, but unless it's marked at 12% and, per gallon, it's less than double the cost of Ultra Bleach, stick with the Ultra Bleach.

You are going to need to add Bleach 3x/day to your water, daily vacuum your pool to waste (a setting on your filter that dumps the water) and daily brush your pool. You'll need to test your chlorine levels 3x/day (use a search to find our Shot Glass Method for rough estimates of higher chlorine levels).

And read our stickies on spring pool opening and fighting algae. EVERYTHING you need to know is posted here.

We'll walk you through it, step by step, but start here. It's enough to begin.

BTW, how deep is the WATER of your pool? You said it was 27'. I assume that means a 27' diameter circular above ground. We need the depth of the water to estimate how many gallons your pool contains, so we can recommend levels of bleach to use.

Ultimately, you are going to do all the work cleaning up your pool, and will make the ultimate decisions of what is best for you. We can only offer you our best advice. The rest is up to you.