Help needed re a bath hot/cold mixer tap with a hand held shower (switched by lever at base of outlet). The instructions state that that water regs require non return valves along with isolators on the h&c feeds. No problem with that. The instructions then continue (not under "regs") "to obtain optimal results......be checked" a) hot & cold water supplies must be balanced b) The cold feed should come from the cold water tank and not the mains c)
Hoping I've supplied all relevant info the question is: Is the requirement at b) normal - I think its stone age Would I get these requirements from Pegler, Bristan etc. (haven't checked if they do anything similar)
b) is standard in my experience. If you have them both from the same header tank then they stay at broadly the same temperature. If one is from the mains and someone turns on the kitchen tap (also off the mains) then you can suddenly get hotter water from the shower and scald yourself.
These dual purpose tap/showers are often given away with a bath suite in other words value is next to zero.
There are 2 key requirements to make your shower work effectively:
balanced pressures on H & C supplies. Dual purpose bath taps cum shower do not have a pressure/balance regulation valve (at least I've never seen one that does). Balancing to obatin a reasonable shower flow rate and a tolerable temperature is simply by adjusting the H & C taps - a hit & miss affair. Balancing is extra tempremental if the pressure are out of kilter, thus the recommendation to supply both from the CW tank..
2 Equipment designed for the supply pressures.
If you have high pressure HW then it might be possible to make your shower work, but you will need a balancing valve to ensure equal supply pressure. Normal purpose designed shower fittings incorporate these & ensure temperature stability even if flow rates change. My guess is that the manufacturer is obliquely saying that the kit isn't up to a high pressure supply.
There's a risk of scalding if flow rate and temperature isn't controlled & maybe the manufacturer is recommending low pressure operation to limit that risk?
Sorry can't help there, but I suspect a satisfactory high pressure unit (if one is available) will not be given away free. One alternative you could consider is a separate electric shower unit mounted on a wall above the bath.
On Tue, 2 May 2006 21:02:38 +0100 someone who may be "PeterK" wrote this:-
Yes, assuming that your hot water supply is fed via a cold tank.
Imagine what would happen if the mains supply failed. Hot water would still be coming out of the shower, fed by the storage tank, but there would be no cold water. For this reason the cold supply should be taken from the same tank, ideally a little lower than the feed to the hot system.
As others have said there is also the question of controlling temperature when the supplies are at different pressures.
Do the instructions give a maximum pressure rating?
The recommendations seem like a complete botch job. Some clearly only apply to mains pressure systems whilst others only apply to gravity fed ones.
For example, a tank fed system wouldn't need the non-return valves, as the tank air break is sufficient to meet water regulations for contamination of the mains supply.
I think the restriction for the cold feed coming from the tank is an attempt to ensure that your supplies are balanced and they are assuming here that you have a gravity fed system, despite earlier demanding non-return valves that a mains system would need.
I have not seen a modern tap that couldn't cope with normal mains pressures. I'd just connect it up to the mains cold supply, assuming you have either a pumped or mains pressure hot supply. If you have an unpumped hot supply, then I would fit a pump. An unpumped gravity shower is like trying to get wet in the Sahara during a particularly long drought.
Spoke to a company involved in the "supply chain" today. Respecting their straightforward and honest answers no further details of identity. Aside from telling me the taps were ok to 5bar the background to the confusing instructions is an allegation there are "a lot" of legal actions in progress between consumers and the "sheds" over water leaks from taps. Some consumers have bought and fitted "bottom end of the market" taps with no thought as to their water pressure and with no legal max pressure in the UK there have been some substantial bursts/leaks. IIRC 15bar was quoted as the water pressure of one complainant. So saying the cold feed should come from the tank and the H & C pressures should balance absolves the supplier of any "high pressure" leak whilst at the same time sneaking in the non return valve requirement to ensure the legality of plumbing into the cold main.
No! Thank you for that posting! It fills in the picture and explains a lot. I'm now not surprised that writs are flying. With the extra info, I would now be extremely wary of feeding mains pressure HW into it.
BTW I don't doubt that any of these units can cope with mains pressure
- it is the ability to mix at mains pressure I doubt.
To add to info in my previous posting, one of these packaged 'free' shower/tap units was fitted in the (new) 2nd bathroom around 5 years ago. It's been on the list to sort out since then, but as it is seldom used as a shower & due to lack of info, the job has been left in limbo. (Well, it was a free lunch..)
The cold tap is plumbed into mains CW and the hot into a gravity fed HW (around 2m head over the taps). The way these units work is either as independant H & C taps or with a flick of a lever send both water streams up thru the shower tube. On mine balancing H & C tends to be hit & miss, but normally because of the excess CW pressure it is far easier to make the mix too cold than too hot. From your posting that's lucky, because it would seem there is a sever risk of scalding if mains pressure HW is supplied.
Basically you have 2 streams of water heading towards each other & what the mix is, is a matter of luck. My guess is that it must be extremely difficult to control 2 water streams in this way, and the greater the pressure the more the difficulty; plus the risk that the cold coould suddenly fail leading to scalding.
Hence it seems to me that this type of bathtap/shower - at least in its raw state - can only be safely plumbed into gravity fed H & C system.
Even with this basic fitting method there's more that need to be done. It is correct as a poster has said that the air gap in the water tank means that SFA the water company is concerned there is isolation (it makes a tundish) between the mains supply and the shower, so a non-return valve is not strictly necessary. However contaminated water COULD be back siphoned into your own private HW system & back into the header tank. Who knows what could start breeding there. You don't want that, so IMHO non return valves are essential in both H & C lines.
A second aspect is the position of the shower head. For the same reason that ought to be restrained so that the head cannot fall into the bath water . That used to be in the regs, but IIRC the requirement has (unwisely) been dropped in the unified (EU) regs.
What else can you do? A quick look in the Screwfix catalog doesn't reveal a relevant substitute combined fitting, but there are a number of separate shower controls you could fit. You could seal off the shower part of your taps and fit one of these units just above the taps. Screwfix cost: most likely in the GBP100 to 200 range. (The key words appear to be 'temperature contriol by ceramic disc'.) Sub-GBP100 (30 up) are listed, but do they control flow and mix properly??)
That's how I'll probably set about fixing mine. Making sure I get proper mix/flow control & I'll probably add a pump into the HW line.
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