Combined tundish

[tonyshouse]

Can a tundish have two inputs from blow-offs/relief valves or should each valve have a seperate dish?

[Nickfromwales]

On an UVC I always put the cold mains PRV and the T&PRV into the same 15mm run. 

The ideal situation if you want belt n 3 braces would be to take each 15mm pipe into a 22mm tee, then to the tundish. On this job i fitted a 22mm x 28mm tundish as the run was around 11m to ground level ( so 28mm discharge pipe ( D2 )). 

Make absolutely sure you have a minimum of 300mm of straight and vertical drop in the D1 pipe before it gets to the tundish. Shorter runs will see a 'swirl' or vortex in the discharged water and it doesn't 'drop' through the tundish at full wallop, eg it sprays against the sides of the tundish and splashes everywhere. Same thing with the D2 pipe which needs to be straight and vertical at least 3-400mm below the tundish before the first turn to horizontal. 

Note the continuos fall in the pipework