Air admittance Valves

[the englishman]

Am I right in thinking that although code allows these devices to be used in North America, any property in which they are used, must have one conventional fresh air vent? Also is it allowable to use a AAV on a domestic sealed sewage pump lift system which requires a 2 ins vent?

[Wgoodrich]

Air admittance valves are allowed by the Code even with the 2" pumped sewage as you discribed. No you do not have to have at least one to open air vent. Air admittance valves may serve totally if sized right. Remember air admittance valves must always be accessible and in a large enough area not to restrict air intake for venting.

Many professional plumbers though frown on air admittance valves looking at them as more nonprofessional plumbing style. Just thought I would add this common opinion in the plumbing trade.

Good Luck

Wg