Nice pump, I like those old IR T30's. Home Depot is always a wash for me when searching for anything other than 1/8" NPT brass fittings. Common copper pipe has an OD 1/8" larger than nominal size. So 1/2" type L,M, or K is 5/8" OD
3/8" type K,L,M and also 1/2" ACR ( refrigeration tube) are both...