So I notice my plumber(s) has used isolation valves which are NOT full bore on my plumbing (See pics).

Whilst I appreciate that taps commonly have a reduced bore within them, I don't really see why these reduced bore valves should be used given they will reduce flow rates, and no doubt there are others placed elsewhere to act as service valves but are flow restricting. It also means my previous measurements of internal flow rates are invalid because plumber(s) are deliberately choking off flow.

I notice when these things are sold it is not made clear that they have reduced bore. The cost of a full bore valve appears to be around £3.50 and a restricted bore one £1.30. The difference is what many people would call insignificant - certainly compared to labour costs.

Is it totally unreasonable to ask for these to be replaced ?

Is there a way to tell the two apart by looking at the valve (while full bore tend to have a lever, the levers are of course removable) ?

Edited Sunday at 14:531 day by Spinny

If you are all on mains pressure the restriction isn't significant - if you are on gravity feed then full bore isolators are the only option as the narrow bore isolators really impact flow.

Thanks marshian, however the words 'isn't significant' is not something I greatly trust coming from most plumbers given the flow issues experienced on my new mains system. From my perspective professionals should not be fitting sub-standard components to systems when the full standard is available for pennies more. The core purpose of a plumbing system is to deliver water flow, restrictions should be avoided not added for no good reason. Plumbers seem to have a tendency to claim every component of a system 'makes no significant difference' then run a mile when the overall system disappoints.

If this is to taps, the taps have restricted flow anyway, so these will make very little or likely no difference.

If they are in a heat pump heating system, that's a different story.

6 hours ago, Spinny said:

Thanks marshian, however the words 'isn't significant' is not something I greatly trust coming from most plumbers given the flow issues experienced on my new mains system. From my perspective professionals should not be fitting sub-standard components to systems when the full standard is available for pennies more. The core purpose of a plumbing system is to deliver water flow, restrictions should be avoided not added for no good reason. Plumbers seem to have a tendency to claim every component of a system 'makes no significant difference' then run a mile when the overall system disappoints.

So what are you experiencing?

As I said they are flow killers on gravity systems but on normal mains pressure systems they are pretty insignificant

I would agree with marshian and JohnMo here, with one distinction. On a normal mains feed to taps, a reduced bore isolator on its own will not usually be the thing that ruins the flow, because the tap is already the restriction. It is a different matter if you have several of them in series, or on a gravity feed or a heat pump circuit, where each small restriction adds up. For telling them apart, look for full bore wording on the body or packaging rather than the handle, as handles can be swapped, and if the flow is already disappointing I would not hesitate to ask for full bore valves on the main runs while the work is still open.