Perko water strainer brass plug:important

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Comment by bob mitchell on March 7, 2015 at 3:23am

Bronze 1/8" NPT plugs are available from www.downwindmarine.com for $3.70. Search for

pipe plug - MNPT square head - Bronze

Comment by bob mitchell on February 27, 2015 at 2:00pm

     When I was checking out my Perko  water strainers both drain plugs were shot. One of them broke off. Clearly there had been electrolytic corrosion. How could that be between two pieces of bronze? Turns out that the plugs were brass, and just looked like bronze because all the zinc was gone. (brass is copper and zinc, while bronze is copper and tin, with some zinc. Bronze relatively corrosion proof, brass is not.) When I scraped the top of one of the old plugs the brass color was underneath. Also, when you look at the threaded hole for the plug above you can see the copper left where the main body of bronze robbed the brass plug of zinc. That was probably over 50 years of neglect, so I don't feel to bad that only brass plugs were available. WHAT WAS REALALY INTERESTING was that the plug has NPT or pipe threads. Pipe thread pipe size diameters do not correspond to their names, for instances on a strainer intake the hole might measure 1 1/2" but it will be specified as 1 1/4 npt threads. I should have thought it was pipe thread, since it needs to seal up, but being that small I did not think of it. Fortunately the counter man was knowledgeable. So the plug measures 3/8, but the tap is specified 1/8" pipe thread with 27 threads per inch! I got a tap as well to clean out the holes. Honestly do not know if they were original, but if yours breaks off you will know what is probably going on.