Shallow traps only use a 19mm water seal and if a full bath empties quickly then the waste water can self syphon the trap empty or if the soil pipe is filled with water, say when toilets are flushing then the water seal in the trap can be pulled (emptied) and let the sewer gases enter the bathroom. Smallest trap seal feeding into a vented stack should be 50mm. Shallow traps are used by installers that want an easy way out due to floor clearance.
Flexi pipes have their uses and when used correctly are more than ok. Using them just to navigate the way to an awkward waste pipe is either just plain lazy or a sign of an installer that wont or can't work his way to the outflow pipe, in solvent weld, properly.
Yes that's a vent in the pic, it can stop gurgling or if there's a vertical run it can help stop the waste pipe self syphoning the trap.
Flexi pipes have their uses and when used correctly are more than ok. Using them just to navigate the way to an awkward waste pipe is either just plain lazy or a sign of an installer that wont or can't work his way to the outflow pipe, in solvent weld, properly.
Yes that's a vent in the pic, it can stop gurgling or if there's a vertical run it can help stop the waste pipe self syphoning the trap.
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