Bath taps for unbalanced supplies

[Ashman36]

Hi there. New diy member here. I am refreshing my bathroom and the taps are currently fed cold mains and gravity hot from the loft. There only seems to be a very small cold water tank in the loft.

I am looking at putting a bath filler mixer tap on the bath but concerned about the unbalanced supply causing overflows and contamination whatnot up in the loft. I have a new ideal standard Tesi bath filler tap from a previous house but this is not rated for unbalanced supplies although is I believe WRAS approved.

Are there many bathroom tap mixers that will accept unbalanced supply or if it is WRAS approved will it accept?

I have found the ideal tempo 2 bath filler (b0730) and tempo shower mixer b0731Aa that mentions accepting unbalanced. I accept most people will either have a high or low pressure setup so retail notes might be limited. In my head I think that although they say it will work it will be awful for temperature adjustment. Especially an unbalanced shower mixer with no thermostatic.

Alternatively I could just get bath pillar taps….

 

[ShaunCorbs]

Individual bath taps these days most taps aren’t suitable for gravity

 

[Ben-gee]

As above, best is separate taps.
I have on one occasion fitted a pressure reducing valve on the cold supply under the bath to dial this back to equal the gravity hot.
This allowed a shower, albeit not very powerful - I wouldn’t recommend this unless there is no viable alternative.

 

[moonlight]

Have you thought about fitting a non return valve on the cold mains side of the tap, that will stop the potential contamination risk. Most modern mixer taps are ceramic and wont work on gravity. You would probably need something with a minimum pressure of .1 of a bar but you might get away with .2 of a bar. Each meter of head equates to .1 of a bar.

 

[Timmy D]

As above, best is separate taps.
I have on one occasion fitted a pressure reducing valve on the cold supply under the bath to dial this back to equal the gravity hot.
This allowed a shower, albeit not very powerful - I wouldn’t recommend this unless there is no viable alternative.

Just adding info about this route and as Ben-gee says, it’s not recommended.

Most pressure reducing valves will only go down to around 1 bar. That’s 10m of head.

If the tank is in the loft and bathroom on the floor below, it’s likely the hot will only have about 0.4 bar pressure, so it will still be unbalanced.

Can’t you pump the hot at 3 bar or 2 bar depending on your mains pressure?

 

[Ashman36]

Ok thanks for the discussion. I’ve used speedfit 15mm to speedfit tap connector for the bath tap as I didn’t fancy copper and or using flexi. This actually gave a decent flow for hot. Great. I had planned to get a plumber to do mains cold. However gave it a go as I can connect after an existing ball valve. However, mains cold when I turn the tap on and off the pipe the moves. The movement is quite a lot of I move from closed to full open (1/4 turn bath taps). No leaks though. And it’s a cycling motion. I’m not convinced that over time on 1/4 turn taps this won’t cause problems. Looks like a cyclic side loading on the fitting. Is this something that speedfit does because it’s not as rigid as copper? And Or do I have to put loads of clips to manage the side loading. I am in spec for the radius.

 

[Timmy D]

Speed fit will move around the oring in the fitting but I can’t understand why turning the tap (if tightened to the bath) would turn the pipe underneath? I may misunderstand you.

Got any pics of above/below?

 

[Ben-gee]

I think he means that when the tap is closed the pipe feeding it moves, that well known phenomenon caused by a shockwave going back along pipe from a rapidly shut mains feed ( usually a solenoid on a wash mac).

Yes, you should clip the pipe if possible - if not you could train everyone to close the tap very slowly, then it won’t happen.

 

[Ashman36]

I think he means that when the tap is closed the pipe feeding it moves, that well known phenomenon caused by a shockwave going back along pipe from a rapidly shut mains feed ( usually a solenoid on a wash mac).

Yes, you should clip the pipe if possible - if not you could train everyone to close the tap very slowly, then it won’t happen.

Yes that’s correct. Reading the John guest guidance the fittings are not designed for a side load. However, there’s no spec stated other than the clip and other distance advice. As it’s just me opening the 1/4 turn tap it sounds manageable.