Hose & waterlock sizing
Two numbers size a wet exhaust: the hose diameter your engine needs, and the water volume the waterlock must catch at shutdown. Enter the engine power and hose length — the tool runs Vetus' own table and formula.
Hose & waterlock sizer
Runs Vetus' published sizing: hose diameter from engine power (at 0.1 bar back pressure), waterlock capacity from their catalogue calculation.
Use the engine's rated power. The result can never be smaller than the engine's own exhaust outlet — that's the floor.
Sizing FAQs
My engine's exhaust outlet is bigger than the table says — which wins?
The outlet, always. The table is the minimum diameter the power needs at 0.1 bar back pressure; the engine maker's outlet is the minimum the engine was designed to breathe through. Never neck an exhaust down below the engine's own outlet.
What hose length do I enter?
The total length of exhaust hose in the system — it's what determines how much water can be standing in the run when the engine stops. Vetus' calculation takes a quarter of that hose volume as standing water and doubles it for safety, which is the capacity figure the waterlock has to beat.
The calculator says ~3 litres but waterlocks come in fixed sizes — what now?
Round up, never down — the next size up costs little and the margin is free insurance. Then pick the family by layout: rotatable connections for awkward angles, LSL for long runs, NLP/NLP3 where you want it quieter, NLPG if combining waterlock and gooseneck saves space. Sailing boats: go up again — rolling engine-off pushes more water around the system.
Does this cover the quiet (LSG/MGP) and high-performance families?
The table here is Vetus' published sizing for the standard LP/MF/NLP/LSS/LSL/NLP-HD families. The LSG/MGP group and the MV check-valve mufflers carry their own published ratings (an MV in 90 mm covers 103 kW, for instance). Tell us the engine and layout and we'll match the family with Vetus' tables.