Does combi boiler need an external pump or not?

[Krzysztof]

My conventional boiler needs to be replaced. One engineer suggested combi with an external pump because water pressure in my flat is low, the other said there's no need for a pump. He even said that if the pump would have a detrimental effect on the boiler. Who is right?

 

[ShaunCorbs]

What’s the water pressure and flow rate of the cold mains ?

 

[Krzysztof]

What’s the water pressure and flow rate of the cold mains ?

One of the engineers checked and said it's 2 bars cold water, flow 4l per minute.

 

[ShaunCorbs]

One of the engineers checked and said it's 2 bars cold water, flow 4l per minute.

Not enough for a combi or unvented what water main do you have eg is it a blue one or an old lead / steel pipe one ?

 

[Ben-gee]

I can’t believe it’s only 4 lpm, was that measured at a tap which has a flow restrictor?
Try measuring it from where the dishwasher or washing machine are connected.

 

[Last Plumber]

Is the set up you have now very poor or are you happy with it?