A home owner called me out to resolve a dispute he is having with a home warranty company over his spa. The spa is leaking and the company subed out to fix it won't touch it because it is wired to the disconnect with Alumunum wire. It is a 50 Amp 240 Volt sub-panel with a GFCI breaker. The wire size looks to be #8 which I believe is too small. But that isn't the issue the company is raising. They are saying the alumunum ground wire is not to code. I might add that from the sub-panel to the spa itself, it is wired with #8 copper and #10 copper for ground. All connections in sub-panel use anti-oxident. Does anyone have any insight into this, or can point me to the right place in the NEC where I can find the answer?