I've been following the interesting discussion about compliance with building regs when connecting a shower trap directly to a soil stack. I haven't seen any reference in the discussions to what exactly is a 'deep seal' trap. When I bought the shower tray, I was sold a McAlpine STW3-R trap as the retailer didn't realise I needed a 'deep seal' trap. I returned it and asked for a deep seal instead and was given a STW4-95. However, I noticed that the depth of the trap was still 95mm. Should I have been given a STW4-R (118mm) instead, as that appears to be a 'resealing' trap, which to me appears to satisfy the regs?