improving cold water flow rate

[paulwgun]

im getting 10.5L per min at my kitchen tap which reduces to 9L/min if i put a tap to run in the bathroom at the same time

I know my pipe run from my outside stop tap is 15mm copper pipe if i was to replace this with 22mm plastic would i get a higher flow rate ?

i want to replace my old combi boiler with a new vaillant 837 so that i can get a really good hot shower flow rate in the bathroom

 

[bolshy]

You can't test your flow rate at a modern mixer tap. Try an outside or standard tap instead (if you have one).

 

[paulwgun]

im getting 11l/m and 9.5l/m on outside tap

 

[bolshy]

You should be getting twice that, or there abouts. I can't see your piping, but you may have an incoming main problem. Check the street isolator and your stop tap are fully opened up.

 

[bolshy]

You say your outside stop tap? The one on your boundary? Or inside the property?

 

[paulwgun]

outside is the WA stop tap which runs in 15mm to my under stairs area where my internal stop tap is located all stop taps are fully open

im going to have to get the pressure tested i think

 

[muggles]

If your static pressure is high but your flow rate is low you have a blockage in your main and upgrading it will be the best option. If static pressure is also low then a larger main will help a bit but not much

 

[bolshy]

Why is your incoming supply to your stop tap 15mm copper?
Is it buried?
Sounds like a DIY set up. Are you sharing with another house?

 

[paulwgun]

definitely 15mm and looks like its wrapped in some sort of tape buried along length of my passage/hall to the stop tap outside my front door

so it looks like ill have to dig up my passage to run a new line in the blue plastic 22mm ?

 

[bolshy]

Yes, you're not likely to improve your flow until you replace this pipe. Even so, sounds like this pipe could already have a kink in it restricting your flow. A new combi will be a waste of money until your flow issues are resolved. Blue PE pipe doesn't come in 22mm. I'd put in 25mm, and change your stop cock inside to suit.