I am rebuilding a bathroom next year and beginning to scope it out. These days finding taps that run on low pressure is quite difficult so I am thinking of replacing the hot water cylinder with one that would take high pressure and taking out the tank in the roof space. I presume it would still be heated indirectly from the boiler which is 1.5 storeys below. That would also solve a problem in the kitchen where the cold is on the mains and the hot is on low pressure. At one time mixer taps were available where this worked (eg KWC) - have they all gone now?
In the bathroom if this is too difficult/expensive I might keep the Ideal Standard brassware - only 27 years old and working perfectly still.
Most kitchen taps these days are of a concentric spout design to avoid this problem (and the need for non return valves to protect the rising main)
From a use point of view, not really - you get good flow rates and (near[1]) mains pressure hot and cold water all round the place.
Lots of detail here:
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However first ensure that you have adequate mains cold water flow rate and pressure before doing away with the storage system.
From an installation and service point of view the cylinders cost a bit more, but come with all the extra controls and stuff required to make them work. They aught to the be serviced annually, although that is well within the grasp of any moderately competent DIYer[1]. They often carry
10 year guarantees, but do require either naturally soft water, or that a scale reduction device be fitted. You can heat them with immersion heaters or indirect coils etc.
(people normally highlight that installing an unvented cylinder comes under section G3 of the building regs, but now that applies to *all* cylinders, unvented or otherwise[3] - so in that there is no difference. If getting one installed professionally then its probably worth making sure the installer knows what he is doing)
[1] Depending on your mains pressure - if its 0ver typically 3 to 3.5 bar then the PRV on the cylinder will limit it to that.
[2] Inspect the tundish to make sire there is no escape of water under normal circumstances. Check the mains inlet filter, Check the operation of the main over pressure and the over temp and over pressure relief valves. Check the air pressure in the expansion vessel.
[3] Apart from small ones for basins etc.
Depends on what size cylinder you want, and how much work is involved... generally speaking you can usually do it by mostly reusing existing pipework. You will need one new run for the discharge pipe.
I paid about £840 for a 250L [1] unistor from a local plumbers merchant...That comes with all the extra bits including an additional Honeywell 2 port motorised valve.
You would be better to keep what you've got. There are no advantages to changing over unless you like high pressure showers. If your incoming mains water pipe is crudded up, you may well find it takes forever to fill the bath with a mains pressure hot water tank. Also you would have moving parts that need to be maintained.
I am gently coming to that conclusion. The water main is fine - the water pressure is huge - and we have soft water so it does not crud up and was renewed in plastic in 1987 (with a big grant from the Council).
As usual harry is, at best, over simplifying. There can be plenty of advantages when a system is installed in appropriate circumstances.
Alternatively you may find with a decent main supply that bath fills become much faster...
In one sense then you have the ideal setup for mains pressure hot water, so it really depends on how well the existing system performs, and what you are attempting to achieve.
In my case there was no contest, the gravity fed system I had previously was hopeless and completely unsuited to the property. What I have now has has proved to be the best hot water system I have ever used, and outclasses the previous in every respect. However that is not going to be the same for everyone.
I've often wondered if there is a good way to safely and legally boost an existing HW tank to work much nearer its rated maximum pressure. Most vented tanks I think are rated to at least 1bar and that would give a useful boost to most systems if you could get the header tank high enough (which in most cases of course you never can - flats excepted).
I guess the problem is providing a fail safe pressure relief system.
Pumps are noisy and relatively expensive. A mains pressure regulator is cheap and quiet. I'm trying to work out whether a long coil laid on its side and with each loop of the coil half filled could provide the necessary "height" but in a compact space for the overflow. Getting 30 ft of height into a coil might need a lot of pipe though!
Ditch the header tank. Connect c/w tank to mains via pressure reducing valve set to 1 bar say. As it's a vented tank you would need a 32 foot high expansion pipe to prevent it just pouring out the expansion pipe (and to stay legal).
Given that that isn't terribly practical, I'm hypothesising whether a vertical coil with say, 32 one foot high segments of water separated by air would exert the same back pressure.
All I know for sure is that an air locked coil of hosepipe if held vertically seems to take a lot more pressure than you'd think to expel the air & water than you'd assume from the simple diameter of the coil. The air locked sections seem to be additive in their resistance.
Go back and read what I wrote. I'm talking about using the pressure capabilities of your existing conventional vented cylinder.
As I said, I think most of are rated to at least one bar (some are higher) and boosting the system pressure to that level would give an appreciably improved HW flow to most systems.
Makes sure the header tank is really at the highest point in the roof space. Often people install them more conveniently lower down resulting in less pressure.
I have seen (some foriegn place) the expansion pipe taken right up projecting beyond the top of the chimney. (With return bend on top) Galv. Pipe There was a reducing valve on the inlet. If it stuck, the water came out of the top & ran down the roof. I think the pressure was about 2bar so about 30ft head. Galv. steel hot water tank I seem to remember. Rivetted.
Hey, you could also use it for your TV aerial as well.
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