We have our first fix pipes in now and I have rigged up a temp sink. It is fed by 10mm hot and cold pipes but at present only the cold is running. The flow rate is pretty slow and it takes quite a bit of time to eg fill a kettle. Our plumber however said its best to match the cold diameter with the hot and we want a 10mm hot to minimise heat wastage and because we will be fitting a boiling water tap anyway. 

So what happens if we swap the 10mm cold for a 15mm cold and keep the 10mm hot? I am assuming this can be done? What would be the consequences? thanks

Get rid of the 10mm and have both 15mm. You need the flow rate.

 

We insualted our long (15m+) run. Means if you go back to the sink a few mins after running the hot, it's still warm enough. Otherwise it's a 10 second wait for hot water. 

Edited December 20, 20232 yr by Conor

That's the obvious solution I agree but its a passive house and I am trying to do my bit for the planet......don't mind a 15mm cold but I would like to keep the 10mm hot

I’m following the same plan as you and for the same reasons - 15mm feeds for showers but 10mm for taps to reduce heat waste. Trying to do our bit for the planet etc.

 

Maybe the way to think about it is to reframe the idea of what ‘a long time’ to fill a kettle means. Perhaps 20 seconds more than usual?

 

It probably feels like an age when standing waiting for the kettle to fill, but compared to the time I spaff away on other things like looking at my phone, I would have to accept that it’s the least time wasting thing I do…

 

You could use the time to practise standing on one leg - good for your balance and future falls prevention!!

42 minutes ago, Omnibuswoman said:

You could use the time to practise standing on one leg - good for your balance and future falls prevention!!

Yep - try it with your eyes shut if you want a real balance challenge - I would have fallen over 5 times filling our kettle!

12 hours ago, Omnibuswoman said:

what ‘a long time’ to fill a kettle means. Perhaps 20 seconds more than usual?

I totally get that but there is a bit more to it - the spray function on the tap for washing veg is also sub-optimal. So what would be good is to hear from someone with plumbing experience on mixing a 10mm hot and 15mm cold.

This is exactly what we have. 

 

10mm hot and 15mm Cold. No issues balancing the flow with a mixer tap. I tried insulating my way out of large dead legs previously and it's a waste of time. The resulting flow rates are about half way down the post. 

 

 

 

 

I spoke to our passivehouse builder this morning and he also said he has no issues with 15mm cold and 10mm hot (which is what he has at his house).