25mm MDPE mains with low flow rate

[All_that_Jazz]

I've been given conflicting opinions from different plumbers about the type of boiler to have installed (which seems the norm reading through the threads), so would greatly appreciate some advice. Some suggest a combi as my flow rate is only 10 L/m and others suggest an unvented cylinder with a sys boiler (along with an accumulator).

I was set on getting an unvented cylinder after someone suggested increasing the mains pipe size to 25mm would double my flow rate. He checked under the sink and told me I have a 20mm mains pipe into my property, but when I had a look (later), it looks to be a 25mm pipe. Am I correct in thinking that (picture attached)? There's a 25 -> 22 marking on the stopcock. It's a bit awkward to measure properly, but seems to be around an inch in diameter.

Does it make sense to be getting a 10 L/m flow rate on a 25mm incoming mains pipe? I thought the minimum with that pipe size was 20 L/m? Would it be worth increasing to a 32mm mains pipe to improve the flow rate and is it possible to exceed at least 15L /m if we were to do so?

The stopcock is also dripping at the gland nut... I have to tighten it almost all the way for that to stop (or reduce considerably).

 

[JohnD]

my flow rate is only 10 L/m

Where, and how, did you measure it?

 

[All_that_Jazz]

I had one local plumber measure from the sink above the stopcock and another from BT used the outside tap. Both had a measuring device.

I also measured later myself with a beaker and stop watch, and it was around the same rate.

 

[Madrab]

Does it make sense to be getting a 10 L/m flow rate on a 25mm incoming mains pipe?

Depends on the district mains, where are you located? I'd recommend you call your water transporter and get them to come out and test the mains and ask them nicely to tell you their dynamic pressure and flow is.
That will dictate whether you have an issue with you mains or not. All things being equal that 25mm MDPE (yes it's 25mm) should happily deliver what the district mains can supply, so it may be that the mains actually isn't the best. They'll be able to confirm.

The dynamic flow and pressure @ your mains tap is what you need - pressure gauge on say an outside tap and then run 2 or more cold taps, one upstairs if possible. Check the pressure reading before the taps are run and then again when they are running. Then fill a bucket at the upstairs tap, over a minute and see how much water is captured - those 2 readings are you dynamic flow and pressure.

Only once they are known can you understand properly what your options will be.