If there is a boiler system, make sure you inspect inside of each radiator to check for corrosion around the valves.

I'd also be inclined to upgrade the panels (I always do) depending on the amperage/condition of the busbar (corrosion).

@Jim Adrian I guess it just depends on which internet site you choose as I found a few that definitely push vinyl over aluminum.That second link even says Vinyl comes with UV stabilizers that work to keep sunlight from breaking down materialhttps://www.stanekwindows.com/vinyl-vs-aluminum-wi...I just see info that aluminum frames are prone to corrosion, cost more, and act like radiators. 

You don't want to have a situation where you close the valve as a test and then it won't open again.Its inside to condo, with visible signs of corrosion on the outside.

Likely corrosion built up in the pipe causing the restriction. 

Water heaters can go longer if they are flushed and the water supply is not either corrosive or has a high mineral content. 

Galvanized inside the house rarely actually leaks or breaks, by the way - the bigger problem is the pipe corrodes so bad internally that you get ridiculously low flow & water pressure from the line, and bits of corrosion break loose and clog internal water passages in appliances, get caught in valve seats, etc. 

Beyond that, you're going to have corrosion inside the lines.

I clean roofs and siding , first add some dawn to the mixture of bleach , it will help it stay on the siding longer , dont get it on the ac unit or in electrical outlets (its corrosive) It will kill plants , all you have to do is rinse them real good .

Remember bleach is corrosive , dont use it around metals , even the vapors will corrode metals.