I would say drain, manually clean/scrub as much as possible, then refill and function test the equipment to make sure it works. Or you could do a quick function test of the pump to ensure it moves water before draining so you don't end-up with fresh water that's going to just sit until the equipment gets repaired. Either way though, replace that spa water. Ensure your friend has a TF-100 or Taylor K-2006C ready to test levels. Hope that helps.