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Hi everyone, just a question for my own knowledge and understanding of how water works in my flat and making sure everything complies with water regulation in the UK. , The flat is circa 1960s used to have a hot water cylinder and cold water tank in the cupboard but since late 90s or early 2000 was replaced with a combi boiler for DHW and CH in the flat.

Does the following seem right and current with UK water regulations and do I need to change anything?
  • Top floor flat, hot and cold is via mains water feed, Combi boiler (8 months old) 1.5 pressure bar on combi boiler.
  • Have mixer taps in bathroom (bathtub and basin) and single lever mixer tap in kitchen, thermostatic mixer shower, all hot and cold pipes in bathroom and kitchen have isolation valves fitted on them.
  • The Main Cold Water Feed Pipe in the utility cupboard has a 22mm Non Return Valve fitted on it.
  • Hot water pipe under kitchen sink has a check valve on it
Do I need to add any NRV's/check valves to any of the pipes in the kitchen or bathroom or does it all seem legit. As mentioned I live on the top floor and have another 2 flats below me.

Any information or advice would really be appreciated as I am interested in knowing how things work thank you.


Gas Engineer
Hi Bobbyjoe,

You have what’s generally referred to as balanced supplies so the hot and cold are of similar if not equal pressure. Providing your taps have an adequate air gap between the spout end and spillover level, then all should be good. Your shower shouldn’t be able to fall into the bathtub or within (usually) 25mm if spillover level, the spillover level of the wash basin, bidet or wc pan.

See this for a bit more clarity:

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