Low water pressure with combi boiler


Postby Chewy 1305 » Fri May 15, 2009 1:33 pm

I want to fit an ensuite shower. The problem is when the current shower is running, which is a mixer shower running of th combi boiler, and you turn on another tap the pressure is lost, so how would I be able to run 2 showers at once. Is it possible to put a pump on the mains water to increase pressure then I could install a electric shower in the ensuite which would run off mains cold water. The mains pressure is quite low anyway. Any ideas
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Postby Perry525 » Fri May 15, 2009 7:56 pm

The traditional system (the best system ever) a low pressure system with cold water tank in the loft will solve the problem for you.
Merely add the hot water tank to your central heating and you instantly have hot and cold water at low pressure at every connected tap, meaning you can run all the taps together as slow as you like or as fast as you like.
Something you cannot do with a combi!
Then add a pump for the shower.
Don't forget a power shower requires a water meter by law.
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Postby rosebery » Fri May 15, 2009 9:48 pm

1. What is your mains pressure? Have you measured it?

2. I don't think you have a pressure problem. I think you have a flow rate problem in the DHW side of your system.

3. I also suspect you have an undersized boiler for your requirement already. Adding another shower to it will just make it worse. What is the make and model of your boiler?

4. You are NOT allowed to pump mains.

It sounds as though an electric shower directly fed from mains is probably your best bet. Bear in mind you'll need a Part P, 17th sparks to do the cabling for you. However, the answer to question in 1. above is really quite important as, in conjunction with the question in 3. it dictates the answers.

Cheers
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Postby Steve the gas » Sat May 16, 2009 5:57 am

Hi,

No you cant pump the mains!
Are you sure your stoptap is open fully?
Your water supplier is obliged to give you water at a minimum pressure.
Get them to check it.

Hth
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Postby rosebery » Sat May 16, 2009 1:39 pm

"The traditional system (the best system ever) a low pressure system with cold water tank in the loft will solve the problem for you."

You maybe 100% correct but he doesn't have that type of system so its a bit moot.


"Merely add the hot water tank to your central heating and you instantly have hot and cold water at low pressure at every connected tap, meaning you can run all the taps together as slow as you like or as fast as you like."

Are you seriously suggesting he adds a cylinder to his combi system and do you understand the difference between pressure and flow rate?


"Something you cannot do with a combi!"

Quite.


"Then add a pump for the shower."

Oh you are suggesting he changes his system then.


"Don't forget a power shower requires a water meter by law"

Please provide reference. Thanks.

Cheers
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Postby htg engineer » Sat May 16, 2009 3:56 pm

Basically a combi will provide water at a good pressure and good flow rate for one shower/tap. Which is all most people (including myself) need or want, if you have 2 or more bathrooms - a combi is not suitable for you.


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Postby H74 » Fri Jul 31, 2009 10:04 pm

I have exactly the same problem; we live at the top of a hill within 1km of the water board station, yet we have 1.5bar pressure coming into the house, apparently if it was higher the folks at the bottom of said hill would have far too high pressure.

We have a Grant oil fired combi boiler and this was on the advice of a recommended and reputable plumber; we have an existing shower which this runs, but we are mid extension in which we had planned to fit an en-suite with shower.

Am I wasting my time, as we do not have the loft space to fit a tank; so is an electric shower my only possible solution, an expanding family forces the need for an extra shower.

Any advice before I order what could be a redundant extra shower.
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Postby htg engineer » Sun Aug 02, 2009 6:47 pm

It wouldn't put me off as an en-suite will improve and add value to your property, it's up to you whether you fit an electric or a thermostatic mixer shower, they'll both have the same problems if both are used at the same time.

Be honest and think it through - would 2 showers be used at exactly the same time anyway ? probably not. All it'll mean is that you have a choice of what shower to use, plus one person can use the shower in the en-suite whilst another is in the bath in the main bathroom etc etc .


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Postby Steve the gas » Sun Aug 09, 2009 9:40 am

Save time and money - shower together 8)
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Postby Perry525 » Thu Aug 20, 2009 3:06 pm

Rosebery - 16.5.09
Sorry, I haven't been back to this earlier.
Adding an indirect copper tank to the central heating is simple.
Adding a cold water tank in the loft ditto.
Using 28mm copper pipe to deliver both hot and cold water ditto.
Result, lots of hot and cold water available for shower, bath fills in an instant.
Wouldn't cost as much as buying a large combi.
Everyone should do it!
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Postby htg engineer » Sat Aug 22, 2009 5:48 pm

So for an efficiency A rated combi boiler, what would adding the cylinder make it ?

'Adding an indirect copper tank to the central heating is simple'

How is it simple, you're expecting a DIYer to install a cylinder and tank, wire up a cylinder stat and three port valve, only way you can control the temperature of the cylinder/heating temperature.

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Postby Perry525 » Sat Aug 22, 2009 7:26 pm

There are many DIY people who have designed and installed their own central heating, built their own homes, built their own cars, boats and planes.
All the information they need is available and a lot of these people are very clever well equipped and what is more they have the time and patience to do a good job.
While the Government may be trying to move us into a service society where every simple job requires a tradesman, a situation where people lack confidence and are encouraged to turn to tradesmen for every thing, there are still those who like to get stuck in. I feel they should be encouraged.
To my mind there is little point in pretending things are difficult, when so many have done so much.
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Postby htg engineer » Sun Aug 23, 2009 6:39 pm

I'm not pretending things are difficult - I'm stating electrics and central heating systems are difficult for an average DIYer.

'There are many DIY people who have designed and installed their own central heating'

There are many that have succesfully carried out DIY gas and electrical work, there are also many where people have been killed - just for the sake of a few quid ???? my main priority is my family, not money. Like I'd imaging the majority of people using this forum.

'While the Government may be trying to move us into a service society where every simple job requires a tradesman, a situation where people lack confidence and are encouraged to turn to tradesmen for every thing, there are still those who like to get stuck in. I feel they should be encouraged'

Simple jobs don't require a tradesman, the majority of DIY jobs don't, but when it comes to Gas, Electric and Central Heating systems, then you do normally require a tradesman.



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