Marcos Canales was having fine sailing on board his Catalina 36 Evening Star as he headed south from Channel Islands, California bound through the Pacific for his home in New Caledonia. He had only had 15 days to prepare for sea after buying the boat, and as he made clear, he was aware that Evening Star had been used mainly for local sailing so he was prepared for a few mechanical problems. What he wasn’t prepared for was water mysteriously coming into the boat when he finally reached the trade winds and began reaching briskly southward. By the time he had checked all possible sources he hit the ITCZ and the light changeable winds found there. The leak stopped. Now he knew it had something to do with being heeled on the starboard tack. Answer? His bilge pump outlet went from the pump, through a loop that went almost to the underside of the deck and then out through a thru-hull on the side of the hull about 14 inches above the waterline. When the boat was heeled, the thru-hull was submerged; the wave action caused the pump to back-siphon, bringing a one inch stream of water into the boat.
To cure the problem he removed the hose from the thru-hull, attached an extra length of hose and lead the bilge pump outlet up on deck to run overboard. Here in Apia, Samoa where we met, Marcos is making a permanent arrangement of this on-deck bilge pump outlet.
We too experienced a back siphoning problem on once on board Seraffyn, even though there was an anti-siphon valve on the high point of the loop for her bilge pump outlet hose. Turned out corrosion in the small bronze anti-siphon valve had stopped it from working – a fish boat went by and set up a big wake, water action started the hose siphoning water into the boat, and, if we had not returned early from an evening out, we might have come home to a sunken boat. As it was, the floor boards were under 14 inches of water, I mean water up almost to our knees!
Thus Taleisin’s bilge pump outlet hose goes through the deck to a pipe that leads overboard above the transom.