During an inspection of a well-built, ocean cruising vessel, the following defective through hull fittings were noted. See report extract below.
On examination of the gate valves for the cockpit drains, it was noted that the valve to port was exhibiting some evidence of corrosion. During operation of these units I noted the handles were stiff and even when the gates of the valves were closed the handles continued to turn illustrating the shaft had sheared. I then tried to back out the gates to open the valve again, and although the handles turned, inspection from below the vessel revealed that the gates remained closed. As the owner was present we were able to take this investigation further and set about dismantling the valves to establish the extent of their deterioration. During our attempt to dismantle the corroded valve to port, the shaft housing of the valve broke off completely, confirming these units, or at least the shaft and shaft housings to be made of a standard brass, which has dezincified. (See pictures).
(Recommendation) Both of the valves associated with the cockpit drains need to be replaced as they were both found defective and made, or partly made of non-dezincification resistant material. It is essential that these items be replaced with BRONZE fittings prior to re-launching. It should be verified that the new fittings that the owner is having installed are suitable for their intended use i.e of bronze or of a similar dezincification resistant material and intended for marine use for application below the waterline.