Non-Return Valve Question.

[Simmo]

Sometime in the past someone has fitted a non-return valve into the feed pipe for a bath tap in a house I've recently purchased. The tap is just a single 'bib' type tap as opposed to a mixer. I'm fine with the principal of a non-return as I worked with hydraulics for many years but am struggling to work out why you would want to prevent a backflow in a single pipe with just a tap on the end? Does it prevent air being drawn in if the bath tap is on and then another cold tap is opened elsewhere or is there another reason? There's a combi-boiler installed just in case that makes any difference?

Thanks chaps.

 

[ShaunCorbs]

tap below the spill level?

 

[Simmo]

Not below the spill level no, in fact definitely not now as I've taken the bath out to fit a shower cubicle I've removed the non-return and capped the pipe until I install a mixer shower etc. Just couldn't establish why it was fitted to begin with.