The NLP Waterlocks are of dual stage construction, featuring upper and lower chambers with a horizontal partition plate and a riser tube through the centre. Compared with single stage Waterlocks using only one chamber, these NLP Waterlocks offer superior silencing of exhaust noise with minimal back pressure. Since the top chamber may be rotated through 360¦ and both the inlet and the outlet connectors can rotate through 360¦, installation of the exhaust assembly even in confined engine spaces is greatly simplified.