Pressure problems

[Nigel 206]

Hi all,
My cousin is living in High Barnet,North London, an area apparently known for less than normal water pressure due to the area elevation.

When she first moved in, the water flow and pressure was quite good throughout the house,hot and cold.

She then had a new Vaillant EcoTec Plus 824 installed in the kitchen right next to a mains supply and stop-cock,and just above the kitchen sink.
The water pressure from the cold kitchen tap is very good, the hot tap is slightly reduced but could easily sustain a good shower.

However, upstairs is an issue. The bath takes 10/12 minutes to fill with hot only, and if you turn on the cold simultaniously,everything dries up to dribbles.

There is a ball-valved tank in the attic which,apparently, only supplies the cold bathroom basin,a remnant from the old system.

Some new pipework was installed when the combi was put in, but no more than deemed necessary at the time.

The CH system is working fine (thru the Vaillant)

She is shortly to be refurbing the bathroom, including a new shower.

My questions are therefore:
Is the Barnet water supply likely to be causing the upstairs problem?
Can the Vaillant be supplied, with a pump inline,from the attic tank,in order to increase the pressure slightly?
Could the Vaillant be supplied from just the attic tank, no pump?
Is the position of the Vaillant an issue? Would it be better situated in the bathroom?

With thanks, Nigel

 

[Mike Jackson]

If the pressure and flow are good at the kitchen sink then they should be okay elsewhere.

Good pressure does not mean that a combi boiler will perform well. Flow rate is important for correct performance. A very high pressure through a small diameter pipe will give a low flow rate but a lower pressure through a larger pipe will give a higher flow rate.

I think the 824 is a 24Kw boiler and should give a hot water flow rate of around 10l/minute. To get a reasonable performance on hot and cold simultaneously you would need a minimum of 20l/minute on the incoming main and preferably more.

At a 20l/min flow rate you would need to think about fitting flow restrictors to the cold outlets to prevent them robbing the hot water.

If the incoming main cannot provide a sufficient flow rate it is possible to feed the boiler from a storage cistern via a pump but not by gravity alone.

Mike

 

[Deleted member 2053]

How long ago was this Vaillant fitted and has the problem been there from day one?

 

[Nigel 206]

Hi Grahame,
It was installed about 2 years ago, and yes these issues have been there
ever since.
Since I posted, i've read that combi's need a good pressure to work well.
Perhaps she got bad advice.

Nige

 

[Deleted member 2053]

The 824 is supposed to work fine at 0.5 bar. Mind you if it was this low at the kitchen sink then it would be about 0.25 bar upstairs which is likely to be a problem. When the CH system is cold press the '-' button on the boiler and see what the system pressure is. If it is less than 1 bar turn on the cold tap to the sink and then whilst it is running open the filling loop taps under the boiler (2 grey taps) to see if you can get 1 bar pressure. (By pressing '-' again as necessary). If you can get 1bar whilst water is being drawn off then the problem is probably elsewhere.

 

[Nigel 206]

That's a great help Grahame.

That test will answer some questions.

Thanks.