What to use to replace this grey piping & purge valves?

I`ve never used the Shark Bite fittings -- Ace Hardware & such should have 1/2 inch barb fittings, & you can use regular hose clamps -- Not the best, but will work -- Get a short piece of PEX pipe for to bridge the gap where you take the low point drains out -- The barb fittings are much cheaper, & bettr than Quest, & Shark Bite -- Let us know how you make out -- It`s not a big job, just the right parts -- Bill Willard