Is a non return valve required on new shower?
- Thread starter Stivino
- Start date
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Won't hurt as long as you can gain access to them.
The manufactures instructions for the shower should tell you.
The manufactures instructions for the shower should tell you.
L
longdogs
I've never really understood why any shower connected to a combi would need non return valves. Hot water is fresh, at the same pressure as the cold and how could hot water contaminate the cold if it's from the same supply?
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because without one when you turn on another hot tap it will be luke warm as you will get cold going back up the hot feed
Why would the cold go back up the hot feed? they are at the same pressure.
It sound to me like this is one of those situations where people here ' some showers need a non-return valve' . They don't stop to consider why, and then it mutates into 'all showers need NRV'
When I fitted a shower to the combi fed system in our old house (circa 2000), I had to fit a NRV because it had a typical flexible hose which could let the head hang down into the tray where the dirty water was - which could contaminate the mains if was to get sypioned back into the shower feed.
But if I had used a fixed head there was no requirement
It sound to me like this is one of those situations where people here ' some showers need a non-return valve' . They don't stop to consider why, and then it mutates into 'all showers need NRV'
When I fitted a shower to the combi fed system in our old house (circa 2000), I had to fit a NRV because it had a typical flexible hose which could let the head hang down into the tray where the dirty water was - which could contaminate the mains if was to get sypioned back into the shower feed.
But if I had used a fixed head there was no requirement
A
AlexCarp
Galoka, that is how I understood it. To stop contaminated water entering the potable water pipes if ever there was a reverse flow for any reason.
In a situation where the cold mains fails and the mains water pipe is emptied, say in a top floor flat and the taps are then opened then the now CAT 2 hot water could be drawn/enter the cold mains pipework, contaminating the cold supply. That's why a recommendation is that a single check valve is installed just after the mains stop cock especially in flats. I guess nrv valves on a mixer shower prevent that happening but at the outlet rather than at the mains in.
It is a bit extreme PC I guess but that the regs for you.
It is a bit extreme PC I guess but that the regs for you.
Been to god knows how many "faulty boilers" where the hot is running luke warm only to find a stuck nrv on a shower, when the hot nrv sticks it allows cold mains to mix with the hot water system,
not all showers close off the hot and cold supplies as they enter the shower body but close off the outlet relying on the nrvs to prevent cross contamination,
not all showers close off the hot and cold supplies as they enter the shower body but close off the outlet relying on the nrvs to prevent cross contamination,
A
AlexCarp
Interesting. How do you diagnose it is the NRV on the shower hot? I would have thought that would be difficult to pin down.
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