Basins' outlets *sealed* onto P-trap ?

Previously the wash-basins here, discharged into the stainless-steel urinals. Importantly the urinals were 'open' ie they discharged into a P trap. Now they are replacing the old urinals with ceramics which have outlets which are air sealed to the old P trap.
My feeling is that such urinals should not be 'sealed' onto a P trap outlet. Clearly there is the back-pressure of the P trap's trap-height to over come. IMO if you had a series of P traps in a sealed circuit, you could potentially have an air lock. I think the P trap 'receiver' must be open to the air.
In one of the installations [opposite my office/cupboard] the outlet from the basin, goes via a shower outlet; and now the basin discharge starts bubbling in the shower floor instead of flowing straight to the lower total outlet. Ie. after the urinals.
Thanks for any opinions.
== Chris Glur.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
Add image file
Upload is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.