Check valve in exhaust system

[BBH]

I have been advised to place a check valve in my to-be-installed water lift muffler system (replacing a copper water jacketed exhaust pipe), but I don't see any mention of doing so in Chapter 7 of Don Moyer's Service and Overhaul Manual.

West Marine has several check valves in their catalog, but nothing specific for wet exhaust systems. Vetus has built-in check valves in several of their exhaust mufflers, but no check valves sold singly that I can find.

Am I being given bad advice to install a check valve? Or should I rely on an upward loop (as a gooseneck) in my discharge exhaust hose just prior to the exhaust outlet at the stern of the boat?

[Don Moyer]

BBH,

You might find differing opinions on this point, but our understanding is that check valves in the exhaust pipe or hose can be quite problematic. We owned a Catalina 30 for several years, and noted that earlier models of the Catalina 30 fleet had check valves in their exhaust hose but later models did not. When we checked in with Catalina customer service, we were advised to not install a check valve, due to the fact that they had caused so many problems related to excessive back pressure, etc.

Perhaps some other folks can check in with more experience in this matter.

Regards,

Don

[B Boudreau]

Have you any new or revised opinion on the instalation of a brass check valve in the hot line section of the exhaust? You last replied to this question 1 1/2 yrs ago, but I see not follow-up threads.

I am having problems in finding or fixing the anti-siphon fitting in the elbow; and threading a, say 1/4 copper line, is no better.

[Don Moyer]

Others may weigh in differently on this subject, but we still have no documentation that anyone has ever successfully used an 1 - 1/4" check valve in the hot section of an exhaust, presumably to prevent water from washing back into the manifold.

We have serious concerns over such a valve elevating exhaust back pressure, and doubt that a check valve would survive the hot exhaust gasses.

Don