Shower trap water seal requirement

[smallsteve]

I’ve just come across the matter of ‘water seal’, which i’d previously never heard of. I’m currently in the process of fitting a new shower and so I’m not sure whether I have an issue here or not.
You will see from the attached picture that the trap pipework feeds into an internal soil pipe and i think that this requires a 50mm water seal? Thing is, the trap i removed was only a 20mm seal and i don’t remember any issues around smell and so i’m confused about what to do!? What is typically done?
I assume that traps with a 50 mm seal are deeper and therefore the tray has to be lifted higher to accommodate it!? If so, the front fascia panel (plinth) will not fit as it is only 80 mm in height.
So, do I need a trap with a 50 mm water seal and if so, how do i create a new (deeper) plinth that will look OK? Don’t like the idea of using wood, for obvious reasons. TIA

 

[exedon2]

You are correct that 50mm is depth of seal given in document H building regulations
If you want to get trap lower just cut floor out underneath it (though obviously not if a joist in way)

 

[smallsteve]

You are correct that 50mm is depth of seal given in document H building regulations
If you want to get trap lower just cut floor out underneath it (though obviously not if a joist in way)

Thanks for taking the time to respond.

Since coming across this issue I have spent a fair bit of time looking at various traps and would I be correct in thinking that the seal measurement is the distance from the bottom of the internal inlet pipe (as attached to the trap head), to the point at which water can overflow from the cup into the outlet mechanism i.e as demonstrated in the attached file?

i’ve looked at many traps, most of which have internal cups that seem to meet the 50 mm requirement, but they don’t quote themselves as meeting that requirement. McAlpine Sell specific traps that do you claim to be 50 mm water seal and so I am a bit confused. Due to it now being a regulation, I wonder if the majority of traps these days are made to meet the requirement, hence the reason they don’t crow about it anymore!? Or, am I misunderstanding matters?

The slight issue I have with the McAlpine trap is that the dome head is 10mm smaller than the original one for the tray and so it is not an automatic choice.

TIA

 

[exedon2]

I would go with the Mcalpine trap we use them, better made than many others can't remember ever having problems with one.

 

[Ric2013]

McAlpine are good.

To be honest, the 50mm quoted is Document H, not Part H, so if 20mm was working and not giving rise to self-siphonage or induced siphonage, it was fine. UK Building Regulations are not prescriptive: the approved documents are a suggestion as to how you could meet the requirements of the building regulations, so the 50mm depth is not, itself, a requirement. As you aren't a building services engineer, you are best to follow part H when possible, but if a manufacturer makes an alternative product for the specific purpose and it works, I wouldn't worry if it doesn't specify have 50mm seal.