Leak tracing / Dye / Colourant

[MRH2]

Hi

Looking to trace a (possible intermittent) leak would like to add some sort of dye to the area and see if it shows up through the ceiling of floor below.

What do you use to add a bit of colour (but won't permanently stain things like shower trays / sealant etc etc)

Thanks

 

[rpm]

Food dye

 

[king of pipes]

Food colouring as above but use sparingly though make it up in a Jug and pour into drainage point . Kop