Hi Guys, we don't need to get into that. I understand both points, and as I do have small children, I like to put safety in place first - although they are pretty good with not messing with stuff they don't know, one can never be 100% certain.
As of now, I might just go with the shut off valve on the main drain for safety and for monetary reasons (a ball valve is about $12 where a 3-way is about 4 times that) since I already have ball valves. As I learn more about pool plumbing I will make adjustments - I don't mind working with pipes, it's kind of fun. This is the first time ever I dealt with plumbing at all. I have always rented, so there was always someone taking care of issues for me.
Going back to my pressure issue,
it's resolved. I first checked the impeller, by hand, and found nothing. I opened the filter, and there it was. The cartridge was totally green from the algae. There was this thick layer of green and dirty - I guess the water clarifier made it worse. I washed it well, but could not get all the green out of it. Put the cartridge back in place, started up, and the pressure is back.
I'm going to clean it up again today to try to get more of that green stuff out. Should I use a product to clear the filter cartridge when it's like this? Hopefully it won't get like this again.
By doing this, I also noticed that my pressure gauge is not working. Could it be clogged as well? Now I'm not 100% sure whether or not it was working before. Since the plastic cover is cracked from shipping, I wonder if something else has happened to it.
Thank you all for your help so far. Really great people here. I'm have I joined in