One of my heater unions is leaking. I purchased new gaskets and thought it would be a simple task. The unions are split-rings that unite the metal heater tube with the PVC threads. I've loosened the 2 screws on the split ring but they wont budge. Can't turn them at all. Tried light taps but still they wont turn. Took both screws out but these things are fused to the PVC. Any advice? I feel stupid that an old mechanic like me can't figure this one out, but I dont want to crack something.

Cal Spas - model: Pacifica - Manufactured Oct 2000
RMF Heater model F2500-0001 - 2"

Have you tried channel locks?

Yeah, I thought of that. Wish I owned a strap-wrench. I'll give it a try. Hope it doesn't crack or my hot tub's out of comission for a week, all for the want of a $5 part. Here goes........!

Follow-up: It worked. Just needed a little nudge and it came right apart (boy do I feel like a shtoop!) Worried that I'd break the split ring but it's pretty tough plastic.

I DID have to borrow an extra large channel lock to do the job. And found out I didn't need to take the little split-ring screws out...just loosen them a turn or two.