Hi,

I'm about to check out tiles for the bathroom, so want to sort the shower &
plumbing first.

Currently I have an electric shower which takes a cold feed and heats as the
water passes through. It's a bit on the slow and drizzly side, so I want to
know what my options are for POWER.

I have a combi boiler which drives most of my hot water needs and there's no
header tank currently installed anywhere.

AIUI I can run a mixer tap+shower direct from hot and cold water supplies
which, given the pressure from the tap at the moment, should be an
improvement on the electric. But if I want real power, then a pump is
required. This is where I get confused:

From what I've read, a pump cannot have hot water fed directly from a combi
boiler. It seems I have two options:

1) Header tank above the bathroom, fed in to pump and on to shower - seems
to be the superior solution, but I don't quite understand how this works. Is
there an immersion in the header tank or does the tank fill up with hot
water from the combi which then provides a reservoir for the pump and
shower? In which case, where does a mix of cold water come in for
temperature control? Or does the header tank store cold water which is
heated somewhere further down the line?

2) Combined electric shower/pump - cold water feed, wall mount unit combines
heater and pump - simpler but not as powerful/hard/fast?

Do I have any other options?

Many thanks!

JustMe wrote:
Hi,

I'm about to check out tiles for the bathroom, so want to sort the shower &
plumbing first.

Currently I have an electric shower which takes a cold feed and heats as the
water passes through. It's a bit on the slow and drizzly side, so I want to
know what my options are for POWER.

I have a combi boiler which drives most of my hot water needs and there's no
header tank currently installed anywhere.

AIUI I can run a mixer tap+shower direct from hot and cold water supplies
which, given the pressure from the tap at the moment, should be an
improvement on the electric. But if I want real power, then a pump is
required. This is where I get confused:


Is that correxct? as long as you have

(a) adequate mains pressure
(b) large enough pipework

You will get a decenbt shower flow,.

If you have

(c) a large enough combi, it will even be warmish..;-)

From what I've read, a pump cannot have hot water fed directly from a combi
boiler. It seems I have two options:

1) Header tank above the bathroom, fed in to pump and on to shower - seems
to be the superior solution, but I don't quite understand how this works. Is
there an immersion in the header tank or does the tank fill up with hot
water from the combi which then provides a reservoir for the pump and
shower? In which case, where does a mix of cold water come in for
temperature control? Or does the header tank store cold water which is
heated somewhere further down the line?

2) Combined electric shower/pump - cold water feed, wall mount unit combines
heater and pump - simpler but not as powerful/hard/fast?

Do I have any other options?

Yes. Scrap the combi and put in a mains pressure DHW system. If mains
pressure is good enough, that will do what you want.

OR shove a cold water pump in the incoming mains to any system that
DOESN't use a header, to improve flow rates


Many thanks!

"Owain" wrote in message
...
JustMe wrote:
Currently I have an electric shower which takes a cold feed and heats as
the
water passes through. It's a bit on the slow and drizzly side, so I want
to
know what my options are for POWER.
I have a combi boiler which drives most of my hot water needs and
there's no
header tank currently installed anywhere.
AIUI I can run a mixer tap+shower direct from hot and cold water
supplies
which, given the pressure from the tap at the moment, should be an
improvement on the electric.

Yes. If you have a 10kW shower and a 30kW combi then you should get
about three times the *flow*. (The pressure will still be the same.)

But if I want real power, then a pump is
required. This is where I get confused:
From what I've read, a pump cannot have hot water fed directly from a
combi
boiler. It seems I have two options:

Correct, for a pump to work you need a source of *stored* and
*unpressurised* hot water.

1) Header tank above the bathroom, fed in to pump and on to shower -
seems
to be the superior solution, but I don't quite understand how this
works. Is
there an immersion in the header tank or does the tank fill up with hot
water from the combi which then provides a reservoir for the pump and
shower?

No and no.

In which case, where does a mix of cold water come in for
temperature control? Or does the header tank store cold water which is
heated somewhere further down the line?

Yes, you would need a hot water cylinder (which can be heated off the
radiator circuit of the combi, if you want it to be).

2) Combined electric shower/pump - cold water feed, wall mount unit
combines
heater and pump - simpler but not as powerful/hard/fast?

No improvement, as the limiting factor is the 10kW available to any
electrically heated shower.

Owain

Thanks for your advice. I have a few follow up questions/clarifications...

To get the best performance from my new shower, you suggest I buy pump+hot
water cylinder alongside my new shower head and mixer taps?

The hot water cylinder can be heated off the radiator circuit. Does that
mean use the same hot water as flows through the central heating - so I'd be
showering in the water that might've passed through all the radiators? Or
does that work differently?

I've had a Google, and these look a lot like the big immersion heaters I've
seen - presumably these can also be heated with dedicated electric
immersion, too? These seem somewhat bulky just for my personal shower use
(single occupancy household) - or am I misunderstanding?

The path would presumably be: Cold water supply - Hot Water Cylinder -
Pump - Shower head.

I assume that the cylinder itself can be located anywhere near to the
shower - can that be above/below/same level, or does it need to be somewhere
specific?

I'm not going to be doing the advanced stuff myself, but will be helping - I
just need to state what I want, up front.

Cheers.

"The Natural Philosopher" wrote in message
...
JustMe wrote:
Hi,

I'm about to check out tiles for the bathroom, so want to sort the
shower &
plumbing first.

Currently I have an electric shower which takes a cold feed and heats as
the
water passes through. It's a bit on the slow and drizzly side, so I want
to
know what my options are for POWER.

I have a combi boiler which drives most of my hot water needs and
there's no
header tank currently installed anywhere.

AIUI I can run a mixer tap+shower direct from hot and cold water
supplies
which, given the pressure from the tap at the moment, should be an
improvement on the electric. But if I want real power, then a pump is
required. This is where I get confused:


Is that correxct? as long as you have

(a) adequate mains pressure
(b) large enough pipework

You will get a decenbt shower flow,.

If you have

(c) a large enough combi, it will even be warmish..;-)

From what I've read, a pump cannot have hot water fed directly from a
combi
boiler. It seems I have two options:

1) Header tank above the bathroom, fed in to pump and on to shower -
seems
to be the superior solution, but I don't quite understand how this
works. Is
there an immersion in the header tank or does the tank fill up with hot
water from the combi which then provides a reservoir for the pump and
shower? In which case, where does a mix of cold water come in for
temperature control? Or does the header tank store cold water which is
heated somewhere further down the line?

2) Combined electric shower/pump - cold water feed, wall mount unit
combines
heater and pump - simpler but not as powerful/hard/fast?

Do I have any other options?

Yes. Scrap the combi and put in a mains pressure DHW system. If mains
pressure is good enough, that will do what you want.

I looked this up on Google. I'm not happy replacing my combi and spending
cash (plus getting builders installing bulky stuff and new pipes) to replace
what otherwise works fine for me - which is what this appears to entail.
It's *just* my shower that I'm looking to supercharge.

OR shove a cold water pump in the incoming mains to any system that
DOESN't use a header, to improve flow rates

I don't need to improve flow rate for running cold taps, hot taps at sink
etc, as these are quite good. I just want a high-quality power shower
solution.

Cheers.


Many thanks!

"Owain" wrote in message
...
JustMe wrote:
To get the best performance from my new shower, you suggest I buy
pump+hot
water cylinder alongside my new shower head and mixer taps?

No; I suggest that you run the shower off the combi hot water and see
how that goes. That should be a fairly minor plumbing job as you only
have to run a hot pipe from the combi to the shower location. (I assume
that mains cold is already available for the existing electric shower,
washbasin etc. You may be able to take the hot from the existing
washbasin etc rather than going all the way back to the combi.)

The limiting factor of such an installation is (a) the flow available
from the mains, (b) the output of the combi. I think the Boiler Choice
FAQ [1] has details of how to measure your mains flow to determine
whether it is likely to be adequate.

If you then think you need more oomph you will have to look at some form
of stored and pumped hot water system. If you have inadequate flow
available from the mains, you will need stored and pumped anyway.

The hot water cylinder can be heated off the radiator circuit. Does that
mean use the same hot water as flows through the central heating - so
I'd be
showering in the water that might've passed through all the radiators?

No.

Or does that work differently?

Ordinary boilers have a closed circuit running through the boiler to the
radiators and a coil (heat exchanger) in the hot water cylinder. The
water in the closed circuit is heated in the boiler, and the heat
transfers to the water in the cylinder by means of the coil. The water
in the cylinder (that comes out of the taps) doesn't go through the
boiler.

Various means of valves, timers and thermostats control whether the hot
water in the closed circuit is circulated through the radiators (for
heating), through the cylinder coil (for hot water), or both, as required.

The combi boiler is exactly the same as far as the radiators are
concerned; it just has the additional function of instantaneous hot
water. You can add additional 'zones' to the radiator circuit to heat
different sets of radiators at different times, or add a hot water
cylinder to the circuit.

I've had a Google, and these look a lot like the big immersion heaters
I've
seen - presumably these can also be heated with dedicated electric
immersion, too? These seem somewhat bulky just for my personal shower
use
(single occupancy household) - or am I misunderstanding?

No, that's them.

The path would presumably be: Cold water supply - Hot Water Cylinder -
Pump - Shower head.

Yes.

I assume that the cylinder itself can be located anywhere near to the
shower - can that be above/below/same level, or does it need to be
somewhere
specific?

The cylinder can be anywhere, but the cold water header tank (which you
would also require) has to be higher than the shower. There are also
some restrictions on where you put the pump.

Owain


[1] Courtesy of Ed Sirett:
The FAQ for uk.diy is at http://www.diyfaq.org.uk
Gas fitting FAQ http://www.makewrite.demon.co.uk/GasFitting.html
Sealed CH FAQ http://www.makewrite.demon.co.uk/SealedCH.html
Choosing a Boiler FAQ http://www.makewrite.demon.co.uk/BoilerChoice.html
Gas Fitting Standards Docs he
http://www.makewrite.demon.co.uk/GasFittingStandards

Thanks a lot for your help.

I'll take your advise and run the shower direct from cold/hot water supplies
fed from mains/via combi to start with - even *I* can install that! I'll
just replace the bath taps with one of those all-in-one bath tap/shower hose
connection things and see how I get on.

Cheers.

"Owain" wrote in message
...
JustMe wrote:
"The Natural Philosopher" wrote
Yes. Scrap the combi and put in a mains pressure DHW system. If mains
pressure is good enough, that will do what you want.
I looked this up on Google. I'm not happy replacing my combi and
spending
cash (plus getting builders installing bulky stuff and new pipes) to
replace
what otherwise works fine for me - which is what this appears to entail.
It's *just* my shower that I'm looking to supercharge.
I don't need to improve flow rate for running cold taps, hot taps at
sink
etc, as these are quite good. I just want a high-quality power shower
solution.

Yes, but the energy requirement of a shower is the product of volume of
water * temperature rise.

If you want *lots* of *hot* water you have to put in lots of energy.

The amount of energy off a domestic electric shower is limited to 10kW.
The amount of energy off a combi boiler is limited firstly by the
boiler, but as even small combis are usually 30kW + that's a significant
improvement on an electric shower, and then by the gas supply to your
house. If you want a really big combi you might have to upgrade to a
commercial gas supply.

A good combi on a domestic gas supply will provide a standard shower
acceptable to most people. However, if you want full-body jets and that
sort of thing, you need more energy input than a combi can provide
instantaneously.

So, if you want more hot water than your available source of energy can
provide instantaneously, you have to heat the water in advance over a
period of time and then store it. This is why a 3kW immersion heater on
a cylinder can give a better shower than a combi boiler of 10x the power
- although obviously only until the stored water runs out, then it's a
wait of maybe several hours for the store to heat up again.

Owain

OK, I'm getting my head round this now - thanks for explaining in a manner I
can understand. I'm pretty sure that the cylinder route is one that I don't
want to follow, and have taken your advise, above.

Thanks again.

On Thu, 06 Jul 2006 20:01:25 +0100 someone who may be Owain
wrote this:-

So, if you want more hot water than your available source of energy can
provide instantaneously, you have to heat the water in advance over a
period of time and then store it. This is why a 3kW immersion heater on
a cylinder can give a better shower than a combi boiler of 10x the power
- although obviously only until the stored water runs out,

Part of the skill of designing a stored hot water system is to
ensure, for some level of confidence, that the stored water does not
run out. This is something of a black art, especially in places like
hotels and hospitals. In a large house it may often make sense to
have more than one cylinder, rather than one large one.

An extreme example of the value of stored hot water systems are
showers for use in case of nuclear contamination. One wants a great
deal of hot water suddenly and a plant to create that amount of hot
water instantly would be very large and very expensive. It is far
better to store the hot water ready for the off, accepting the
standing losses.

then it's a
wait of maybe several hours for the store to heat up again.

Though that does depend on the heating strategy. For daytime use the
immersion heater should get the top part of a cylinder up to
temperature in 30-45 minutes. If it doesn't then more cylinders or
more heaters may be desirable.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54