Overflow bath fillers - any that work OK on low pressure sys

16 Feb 2005
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United Kingdom
I'd like to fit one of the overflow bath fillers with deck mounted valves, like this sort of thing:


Yet every one I see says 0.5bar minimum. I have gravity feed system with approx 2m of head pressure to where the deck valves would be fitted, so giving me 0.2 bar ish.

Why is it that they need 0.5bar, do they have exceptionally small pipework? In practice would they not mix very well, or just have poor flow?

I'll be using a pump for a shower, but wasn't sure if I could use the pump (Salamander CT50 1.5bar) to run 2 circuits, but if I could this would give enough pressure.
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Bristan make some overflow bath fillers that require a minimum of 0.3bar pressure, which is about the lowest I've seen on these. They are available from PlumbCenter, and they did have an offer going on these.

You could, in theory use a shower pump to boost the pressure, but much more suitable would be a whole house booster, or single appliance booster by the likes of Grundfos.

The reason these mixers need a good pressure, is they have small bore flexible hoses from the tap heads going to the bath filler, these restrict the flow considerably.

Good luck with whatever you decide to go for!
Thanks for that, a whole house booster pump isn't really suitable at the mo, but maybe an idea for when I have the boiler changed.

I will have a look at the Bristan ones, and as I have around 2m head maybe they will be fine?

I could always swap the pipe for bigger bore ones although I suppose the fittings & internals will still restrict flow.
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They will work fine with the pressure you have at the moment, it may just take a while to fill your bath. Swapping the hoses for bigger ones is not an option really, most can take a maximum of 12mm only. These types of mixers are ideally suited to high pressure systems, unvented hot water systems for example. You could upgrade to an unvented cylinder fairly easilly, and may not even need a new boiler. Your best bet would be to do some research, then get a professional in to give you a no obligation quote. Make sure you get a few quotes before you agree to anything though, and make sure they are qualified to fit unvented hot water systems, even if they are only giving advise. How can someone give advise on something they do not fully understand?

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