On the off chance that someone here still knows... I’ve got a question. I need to know what filter fits in this hot tub. I was recently given one of these old Discovery spas SL800 and I can’t figure out which filter it needs. It didn’t come with one and every hot tub store I’ve been to says they don’t know. Everything else seams, miraculously, to work fine with this 27 year old hot tub, that hadn’t been plugged in for at least 5 years. Any knowledge one of you could pass on would be greatly appreciated.