Through hull fittings.
Tony, You might want to consider upping the size of that through hull fitting to 3/4" because I hope you're also replacing the valves at the same time. I also hope that you're replacing all old gate or ball valves with proper seacock valves. That said, there are no seacocks that I know of made smaller than 3/4" which would sort of solve the problem of finding a 1/2" fitting if it were my boat. You can make new pads of 3/4" or 1" plywood saturated in a good epoxy like West System 105. To clear up any confusion you migh have over the definition of seacock vs a ball valve, the majority of seacocks are ball valves but have a straight thread on the flanged bottom and a tapered pipe fitting on the top designed to allow full seating of the flange end onto the pad by threading all the way down the through hull fitting's straight threads. Note: You might have to cut some of the threads from the through hull fitting to prevent it from bottoming out on the underside of the ball assembly in the seacock. You see, the much cheaper ball valves have tapered threads on both ends and when threaded onto the straight threads of the through hull fitting, will typically only grab 1 1/2 to 2 threads before cross threading, a very serious potential for failure from even a slight side blow. What can happen you say? The valve can snap off the threads very easily and allow a full flow of sea water to enter the boat. The remaining threads in the valve when removed could be likened to a large diameter finger ring, all that saves you from a great day on the water and the possibility of loss of property or lives. So the bottom line should be to get a 3/4" through hull fitting and matching seacock. Good luck, Glyn Judson, E31 hull #55, Marina del Rey, CA
. The old water intake was 1/2. I increased size to 3/4" adding a Groco Strainer and distribution for engine and raw sink/water maker... You can download excellent Groco tech specs from