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increase hot water pressure |
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| message from harry on 24 May 2004 |
Hello,
Does anyone know how you can increase hot water pressure without
increasing the tank size or position or increasing the pipe size. I
was thinking if there is pump that you could add to the hot water
supply to increase the speed of the hot water flow. This is for an
open vented system.
Many thanks
Arif
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| Christian McArdle replied to harry on 24 May 2004 |
Yes. It is called a single impellor shower pump. If you're pressurising the
whole house with it, get a good quality heavy duty type such as a Stuart
Turner Monsoon. Depending on the layout of the system and myriad other
factors, you may find the increased flow rate leads to air being sucked down
the vent tube. If this happens, and there is no obvious culprit like a half
closed feed valve to the cylinder, you will need to install a flange on the
system (or you might find turning the pump down fixes it). The flange will
normally eliminate the air effect provided it isn't too bad, although it
will effectively reduce the size of your cylinder slightly as the top of the
cylinder will become "dead" space.
Christian.
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| A E May replied to Christian McArdle on 24 May 2004 |
Good point about the flange. I've been researching these. I bought a 22mm
surrey flange from PlumbCenter, only to find it doesn't fit on the top of my
"Superlag" cylinder (from 1991). So I plan to make my own flange - I've
bought a 22mm/22mm/22mm Tee and a 22mm/15mm reducer. The T goes on top of
the cylinder. The reducer goes on top of the T. I can file the reducer's
insert limiter rim so I can push 15mm pipe all the way through it, and
through the attached 22mm T (so that it goes under the surface of the water
of the cylinder). It's not a surrey flange - the 'air free' and normal hot
water positions are exchanged. But a coupleof elbows and I can sort that.
You can hear the air in the cylinder if you bang it - and your can hear it
coming out the shower head. But I'm more concerned that without a flange the
pump will suck air down the expansion pipe, rather than out the cylinder!
I haven't ordered the shower pump yet, but I'll go for a Stuart Turner one.
Just 1 bar (that's 30ft head - plenty for me). I want a brass pump -
something that won't split open and flood my house out when I'm at work. The
plastic pumps from local DIY stores look too flimsy - I don't trust them -
the fittings look like garden hosepipe connectors.
Alistair.
"Christian McArdle" <cmcardle75@nospam.yahooxxxx.co.uk> wrote in message
news:40b20f93$0$25319$ed9e5944@reading.news.pipex.net...
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| BigWallop replied to harry on 24 May 2004 |
A normal central heating pump can be fitted in the outlet of the hot water tank
to increase the flow. But you need to fit a flow switch device that detects
when the water is being demanded so that the pump isn't running continually.
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| Tony Bryer replied to BigWallop on 24 May 2004 |
Surely you need a bronze pump not a normal £30 one??
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| BigWallop replied to Tony Bryer on 24 May 2004 |
To Andy and Tony.
I was only trying to help with the question the OP (Harry) posed, and the best
solution I thought of was a standard central heating pump with a flow switch
control arrangement. These standard pumps have lasted on our own system for
anything up to 10 years, so I was not under the impression that a materials
change to said pumps would create any massive increase to their performance or
longevity in these circumstances.
My thoughts are that the standard pump cost is small and the length of time it
lasts in this type of environment outweighs the costs of installing a more
expensive pump which gives such a small increase in the life span of the unit.
My research into the subject has shown me that the standard central heating pump
has a life span of up to 10 years, while the bronze units are rated as having a
life span of 12 years. To me, this small increase in the longevity does not
justify the greater increase in cost of installing this type of pump on to a
system which will not have a continual flow of aerated water, but will only
supply a small amount of water over very short periods of time.
The standard pumps are fine as long as they are installed in a position which
keeps them internally flooded. The water flow through the pump from a storage
cylinder is not interrupted by massive increases in aerated water, so the
impellor unit on a standard pump is more than capable of withstanding these
small deviations and will work quite happily for many years in this situation.
So, in summary, although I disagree with the suggestions you've made on the type
and construction materials of the pump required in the situation that the OP
(Harry) has, I will leave it to his own research into the matter to prove
otherwise.
The just of this posting is similar to a letter I have to compose to an
architect. Does it sound OK ?
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| Andy Hall replied to BigWallop on 24 May 2004 |
The conditions are different though. The CH pump is in iron/steel
because it can be. The water is essentially anaerobic after a few
days - i.e. dissolved air is driven out. With the addition of
inhibitor, rusting can be essentially eliminated.
It will always be in contact with water containing quite a lot of
dissolved air, even if the water has stood in a roof tank for a few
hours, so it will deteriorate in a much smaller time period than 10
years.
The manufacturers make pumps for DHW and potable water use in bronze,
brass or plastic (or even stainless steel) for a reason......
We're not talking about the water being grossly aerated because the
pump innards are partly out of water, though. Just having it in
contact will cause rusting quite nicely.
Yes it does. What do you want him to do for you though?
.andy
To email, substitute .nospam with .gl
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| BigWallop replied to Andy Hall on 24 May 2004 |
<<<snipped>>>
The letter I need to write is about equipment that is going to be installed
alongside other electrical stuff that will cause interference on it, so I want
him to consider a change in the materials he wants used for the installation. I
know that the change will greatly increase the life span of the new equipment,
so I would like him to understand the benefits of changing it now before it's to
late.
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| Andy Hall replied to BigWallop on 24 May 2004 |
Ah, I see.
I wonder with architects how much skin they have in the game after the
project is complete though. Do they design for form or function?
Let's hope he doesn't do airport roofs......
.andy
To email, substitute .nospam with .gl
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| BigWallop replied to Andy Hall on 24 May 2004 |
This architect, a lady btw', has designed everything in this site, right down to
the head colours of the screws that hold the knobs on the doors, and the really
funny bit is, she sounds French and has the surname Le Boussier. So who knows
what else she's been involved in. :-))
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| Grunff replied to BigWallop on 24 May 2004 |
I think you've misunderstood the reasoning. In a CH system, the only
reason the iron/steel components (pump, rads, boiler water jacket etc.)
last more than a few months is that it's a closed system.
You start off with a set amount of water. In the first few weeks, all of
the oxygen in this water gets reacted out. The water by then has zero
dissolved oxygen, and is limited in the amount of corrosion it can cause.
But if you had a constant supply of fresh water the corrosion would
carry on at the same rate. Within a few months there weill be very
little iron left.
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| Ed Sirett replied to Grunff on 24 May 2004 |
I have had mixed results with using iron pumps for DHW boosting and
circulation.
In two applications I replaced the previous iron with a new iron pump and
all was well. Perhaps the water heater had managed to undissolve all the air
from the water before it met the pump?
In the other application I was taken with the 'its wrong but its five times
cheaper and does the job' argument. I installed an iron pump only to have
to replace it with a bronze one a few weeks later due to discolouration of
the water.
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| Pete C replied to Ed Sirett on 24 May 2004 |
Hi,
Installing some sort of anode upstream by the pump could help, BES
part no. 12242 might do though it's zinc and not magnesium which is
better. A section of 22mm or 28mm pipe with a nice big lump of
magnesium fixed in it would do the trick.
Apparently these devices work for central heating systems too:
http://www.scalemaster.co.uk/hcc/hcc_physical_pages/hcc_physical_home.html
cheers,
Pete.
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| Andy Hall replied to BigWallop on 24 May 2004 |
Good idea in principle, but not using a standard CH pump which will
rust as a result of an ongoing flow of water with dissolved air.
For HW applications, Grundfos, among others make a brass pump and this
should be used.
.andy
To email, substitute .nospam with .gl
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| harry replied to BigWallop on 25 May 2004 |
Great for the info, but can i ask, how low shoud the pump be position
from the hot water drain off from the cylinder, and where can i get a
flow switch device and where do you connect this device as well as
wiring such an item. And is it really necessary for a flange.
Appreciate the answer so far.
Arif
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