Volvo D1-30

[All_at_Sea]

This engine works fine but it does have a water outlet on the side of the boat linked to the water pump, the freshwater pipe has a join in it that has a T piece which goes to the side of the boat. Is this normal?
Temp is fine whenever we run the engine.

 

[Tranona]

Nothing should come from the freshwater circuit except to a calorifier - it is a closed circuit. What you are describing sounds very much like an anti syphon loop that goes in the saltwater circuit downstream of the pump. The wter bleed shows the seawater is running but more importantly when the engine stops it lets air in and breaks any syphon. Sometimes they have a valve, other times like yours a "piddle tube" overboard or into the cockpit.

Almost universal so not unique to the D1 30 - have the same engine and mine has a valve.

See thread below which says the same thing, but takes 2 pages!