Boiler gas supply pipe sizing

[struc]

C'mon fella fess up, you're doing this job yourself!!

hmm, I’m starting to wonder if you're just winding me up. I'm not really sure what it is about what I’ve said that makes you think I’d be doing the job myself. Granted, if I was asking about some practical aspect of doing the job but querying the pipe upgrade quoted by a tradesman is not exactly out there in the fields of improbability.


The whole thread wouldn't really make sense anyway, I can clearly do the calculations myself, which isn't that surprising, it's pretty simple stuff, so if I’m not genuinely confused by what I’ve been told by the tradesman what do I actually gain from this thread. Which leads me to conclude that this is either some sort of wind up that I don’t understand, or you’ve just not actually read the thread

 

[adlplumbing]

Gas sizing is a technical aspect of our trade, you are asking technical aspect of it.
As such you may be trying gain technical help, to fit a boiler.

 

[Agile]

Seems my post was somehow invisible!

 

[struc]

Gas pipe upgrading can sometimes be done cleverly by using 35 mm near the meter where there are lots of elbows and leaving short lengths of 22 mm in situ.

But even if a little low like 2 mbar pressure loss, the boiler will work fine. The risk is solely that under the warranty the makers have an excuse not to cover it. But of all the makers, Worcester are probably the most accommodating on installation defects.

Although replacing the water pipe will certainly improve matters, I am a little concerned that, whilst you have grasped gas pipe sizing you seem not to have understood the requirement for a dynamic supply flow rate. You have quoted an open pipe flow rate! But many plumbers don't seem to understand this either so don't feel bad about it.

A shower head will only work and give that fast ejection speed, which gives that tingly feeling on the back, when the pressure in the head is still say 1.0 bar. So what is important is the flow rate that can be achieved whilst leaving some pressure in the supply to overcome the pressure loss in the boiler and shower head.

So you need a pressure gauge ( about £12 in Toolstation ) which you connect to say the washing machine supply tap and then you see what flow can be taken from the taps whilst leaving 1.0 bar on the gauge.

Tony

Thanks for that Tony, I had thought about the dynamic pressure in the past, but had put it to one side for various reasons. I can't actually find any the pressure - flow rate data for the showers we're looking at, beyond them saying min 0.5 bar. The guys who are designing and installing our bathroom didn't seem concerned (cue the barrage of post that I’m actually installing the bathroom myself). I kind of lazily came to the conclusion that once the supply pipe is upgraded my pressure and flow rate is what it is and there's not really anything I can do to improve the dynamic pressure. I guess changing water pipe diameters in my house but they seem to be standard sizes anyway. Do you think my suck it and see approach is naive and something I may regret?

 

[struc]

Seems my post was somehow invisible!

ha, i did almost loose it in all the noise

 

[Agile]

Yes, I know what you mean!

In practice you have little alternative apart from fitting a new supply and that should use 32 mm pipe as its less resistive than the smaller size often used.

But even so I would be interested to know the current dynamic flow rate.

If the shower maker says a minimum of 0.5 bar that means that in practice you need about 1.0 bar to have it working nicely.

The supply pressure also has to overcome resistances in house supply pipes and hot water heating appliances as well!

Bathroom fitters never seem very interested in the technicalities of the supply. They have already got the contract and if the performance disappoints they just suggest you spend further money!

Tony