Megaflow Query

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I've found that monobloc mixer taps (the sort which have just one fixing hole through the sink or basin) especially with ceramic disks (quarter turn) can restrict flow where there's not much pressure. Do you have a washing machine (or connections for one)? If so I suggest that you test the flow at its hot pipe connection (the little tap with the red handle) (after disconnecting the washing machine, natch). If you get a good flow from the washing machine connector the problem is probably with your taps or the flexible hoses, if not then there could be some restriction in the pipework elsewhere.

Yes and no: it will be better, but not as much of a difference as you seem to be describing.
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It depends on what sort of hot water cylinder you presently have. If it's a 'Fortic' or similar (which are common in flats) which has a little storage tank built-in above the hot water cylinder (visually: has more of a flat top than a domed one, and a sort of waist about a foot down from the top) then a power shower would not be a good idea for the risk of running the supply dry and ruining the shower pump. If it's not a Fortic type then you should have a separate cold water storage tank: these are usually in the attic in houses.
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If there is a good cold main flow, then not problem. The cold mains will probably fill up faster than the pump can draw-off water with the cold water stage acting as a good buffer. I have fitted a number of these and used a 3/4" ballcock and 22mm colds mains pipe to ensure the cold tank is filled zippo. Then the Fortic acts as brake tank. There are Fortic which have larger cold tank sections in the unit.
The best arrangement is a Fortic heated via a combi and the combi only supplying the shower giving high pressure showers. The water section parts of the combi last longer as the shower is onkly used a few times a day. Excellent flow at all taps and high pressure at the only point where you need it......the shower. A highly cost effective way of having a high pressure shower, high flows to a bath, no tanks in the loft or cylinder in the airing cupboard. It is cheaper than a megaflo setup with problematic high pressure storage, and a heat bank too. The best solution when installing a new system.
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It is all down to what the plate heat exchanger can take. Most are about 10 bar, max. This is another advantage in that no pressure reducer is fitted.

Just add plate heat exchangers (not very big) and it will give you more than the Megoflo as no pressure reducer is fitted.

Not an issue really.

That is true. A good heat bank with a well sized boiler can virtually heat the store faster than what is extracted. Another advantage: a directly heated bank can take any sized boiler as long as the flow and return pipes are large enough. In fact two cheapish 80,000 Btus boilers can be fitted directly to the store with their own flow and returns for a zippo heat up (A Worcester 82,000 Btus heating boiler can be had for 534.63 Including VAT each, 1065 for two. Or a Glow Worm 30HXI condensing boiler for 663.88 Including VAT each, 1328 for two). That is, if you draw off water below approx 24 litres/min, the boilers will be re-heating faster than you draw-off - great for two showers as you "never" run out of hot water. Then you can downsize the heat banks cylinder size, saving money on the store costs to compensate.
An unvented cylinder is limited by the coil size. Some unvented cylinders can take nearly 200,000 Btus of boiler heat, but they are usualy very large and very expensive.

But if you have 10 bar to spare it is not utilised. All academic, as 40 litres/min is more than adequate for most homes, filling a typical 100 litre bath with 43C water in about 2-3 mins or so, which no one would complain about.
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Heatrae Sadia recommend an absolute minimum 20lpm flow from your mains for the Megaflo. This is definitely on the low side of what you should be using. You are certainly limited by the maximum flow from the mains, rather than the system inside your house. As a very rough guide for the maximum flow rates for hot water you should expect for mains pressure systems:
Combi boiler (non-storage): 10 lpm Heat bank: 40 lpm Unvented cylinder: 75lpm
Obviously, these will vary a lot between manufacturer and boiler power etc. However, none of these systems can provide more flow than your mains supply. If you only have 20lpm from the mains and it is not practical to upgrade the supply, then a combi might be more appropriate than an unvented cylinder (being cheaper and smaller).

Shower hoses and heads are notorious for slowing down the water. In particular, if they are designed for combi boilers, they will do their best to reduce the flow below 10 lpm for more reliable operation. It is possible to get wider bore hoses and bigger holes in the shower head if your system can provide a greater flow. If the shower head was designed for an electric shower, it would have an even slower rate.
Christian.
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"Christian McArdle" snipped-for-privacy@nospam.yahooxxxx.co.uk wrote in message

Many thanks for all the helpful info.
What's the reply likely to be if I call Severn Trent and ask them to turn the flow up?
'Of course, how high would you like?' 'Of course, that'll be a 50% increase on your current 90/month water bill[1]' 'Bwahahahaha'
or something else?
[1] Bit of a bugger when the meter reading sensor thingy was never actually connected to your water meter and you end up paying for three years usage in one.
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20 lpm will almost certainly be within what they consider to be their contractual obligations. It is on the poor side of normal, but not as bad as some get. Your only hope is that the problem is between the street and your cylinder. Compare with other nearby houses to see if they are any better. Make sure the stop cock is fully open. Make sure they piped the main run to the cylinder in 22mm and your main supply to the stop cock in 25mm MDPE.
My fear would be, however, that the entire district suffers from low pressure, as a new house will have a new water supply anyway.
Christian.
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These can go up to 22 litres/min. The average fitted is now is about 12 litres/min

If the mains delivers 75 l/min it can give it. Just add plate heat exchangers.

Average? Please? With 3.5 bar max.
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On 16 Sep 2003 03:13:21 -0700, snipped-for-privacy@coventry.ac.uk (Julia Mann) wrote:

Again, it depends. How much hot water do you need to store? See here for a guide to prices:-
<http://www.discountedheating.co.uk/shop/acatalog/Online_Catalogue_Heatrae_Megaflo_HE__Indirect__112.html

Hope this helps
Neil
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