What method of hydroponics?
what plants?
what size reservoir?

You will have to do some of your own search on hydro and your questions are far too general to have specific answers.

I plan on using a N.F.T. method using gutter drains. I using a basic rubbermaid container for the nutrient rev..So basically pump comes one runs downhill down the gutter and back to the tank so that's it. I have heard so many stories about then ph going whacko if u don't change it or at least adjust it once a week. Any comments or replies are appreciated.

Depending on the volume of nutrient solution compared to the size of the plants, you can see some pretty massive pH swings in less than a day. The larger the reservoir the more stability you'll see, but obviously that means it takes more nutrients for each refill.

I would say that changing the nutrient solution every 3-5 days is a bit of overkill. It's not that tough to check the pH with the paper strip testers and you can save yourself quite a bit on nutrient expenses. Totally up to you of course. I'm just lazy and don't like the work of exchanging that much solution.

But yeah, your pH can go totally wonky in a day or two if you don't keep an eye on it - just changing the solution every few days won't safeguard you against that.