flow rate

[inspectorgadget123]

just had my system changed from a gravity system to a combi system.
when we had the flow rate checked at the mains it was around 27 ltr p/m.
now our combi system is in we are getting 12.5 ltr although the boiler should give 25ltr as it is a 550cdi highflow.

is this normal ?

 

[kevplumb]

is the cold water isolater on the boiler fully open

 

[inspectorgadget123]

not sure where would it be ?

 

[kevplumb]

underneath on the cold pipe

 

[inspectorgadget123]

seems to be fully open

 

[Joe4542]

Have you re-checked your cold mains flow rate now? ie at the kitchen tap or Garden tap?

Fill a bucket etc and time it.

 

[inspectorgadget123]

garden tap seems to be 22 litre p/m which i actually think was the correct figure.

so i am losing 10 litres a minute .

could this be incorrect plumbing of the combi ?

i have a suspicion that the cold feed was picked up from upstairs just before the old tank in the loft , so i assume the water comes from the mains to upstairs then back down to be heated then up again to the shower .

 

[Joe4542]

Well given that flow rate, unless you have really bad pressure, you should still get most of the 22L/min.

Does sound like problem with piping, Ensure any service valves around boiler are fully open - including the service valves inside boiler casing (front @ bottom).

The pipe shouldn't be tapped off the feed that went to the loft, it should be piped off the mains at ground floor - ideally before any major restrictions or other draw-offs.

In your last post you mentioned boiler feeding shower - when you're checking the hot water output it should be the same (roughly) as that from cold in similar position. So no good expecting same flow from shower on second floor compared to cold mains at ground level for example...

Check flows at kitchen tap on hot + cold, is hot still significantly lower there?

 

[inspectorgadget123]

Well given that flow rate, unless you have really bad pressure, you should still get most of the 22L/min.

Does sound like problem with piping, Ensure any service valves around boiler are fully open - including the service valves inside boiler casing (front @ bottom).

The pipe shouldn't be tapped off the feed that went to the loft, it should be piped off the mains at ground floor - ideally before any major restrictions or other draw-offs.

In your last post you mentioned boiler feeding shower - when you're checking the hot water output it should be the same (roughly) as that from cold in similar position. So no good expecting same flow from shower on second floor compared to cold mains at ground level for example...

Check flows at kitchen tap on hot + cold, is hot still significantly lower there?

it seems to be 12.5 litre everywhere hot and cold regardless of upstairs or down. only the garden tap is 22 litres

 

[doitall]

In that case you have a restriction, check the pipe sizes, filters, and even fixtures and fittings, especially flexible hoses, and any isolating valves.

 

[Joe4542]

As DoItAll says, this suggests the problem isn't neccessarily the boiler since your cold is also suffering - and this does not pass thru the boiler on way to cold taps.

Possibly you have more than one stopcock and the garden tap is fed after the first one, and the rest of house brances off after another - that may be partially closed.