Hello Dizzle, and welcome to the forum!!

Congrats on the new house and pool, and I'm impressed that you've done your homework as far as pool maintenance. You'll find that controlling your own pool will make life MUCH easier and the pool much more enjoyable.

In answer to your question, yes, the only practical way to lower the CYA is to do a partial drain and refill. You can up your chlorine levels to compensate for the high CYA, but yours is high enough that even that option is iffy at best. With this being the beginning of the season, I very strongly encourage you to drain/refill as much as you can to get that CYA down to the 40-50 ish range. You may need to do that in a series of smaller drain/fills, but that will work too. If you decide not to lower the CYA, keep in mind that you need to keep the chlorine at a minimum of 8 ppm to keep the algae away. You can get away with 5.5 for right now because the water is cold, but that won't last long, and since you just got it cleared up, I would hate for you to have to fight another outbreak this soon. Once your water temp gets above the mid 60s or so, you're going to need to get the chlorine up or the CYA down.

Your TA is a little bit high but not high enough to worry with right now--when you start adjusting pH, the TA will adjust with it.

Again, welcome to the forum and I look forward to seeing you around.

Janet