HH56 wrote:
Finding the female fitting in 5/16 seems to be the issue since that size seems to be a not heavily used item and appears to be discontinued. If you can find some old stock like this fitting where you normally shop or are getting the others you could eliminate the coupling and extra adapter. Space is somewhat of a consideration since there is a fairly short distance between the tube end and pump to route the hose to avoid kinks. Time you find and get all the materials, with your time plus their cost and the freight it would probably be as cheap to buy a finished hose from Max.