Low gas pressure

[Simon F]

Pipework from meter is 22mm, goes in house and under floor in 22mm approx 3-3.5m. Comes out of floor where boiler is in 15mm.

no one else seems to be asking this so.
does the size change from 22 to 15 at some point under the floor?
how much 15mm pipe is there?
that will starve the flow dramatically!

 

[jaydebruyne]

no one else seems to be asking this so.
does the size change from 22 to 15 at some point under the floor?
how much 15mm pipe is there?
that will starve the flow dramatically!

It changes under the floor and no idea where.. so going to replace the rest of the run with 28 until it hits underneath the boiler which it'll then be 15 for about 500mm and tee off in 15 for the hob for about 1.5m

 

[Simon F]

sounds like that's the problem then,
run the 28 as far as practical then 22 straight to the boiler

 

[jaydebruyne]

sounds like that's the problem then,
run the 28 as far as practical then 22 straight to the boiler

Will be doing it Saturday. Cheers Simon

 

[Last Plumber]

no one else seems to be asking this so.
does the size change from 22 to 15 at some point under the floor?
how much 15mm pipe is there?
that will starve the flow dramatically!

I've asked about the 15mm!

I also asked about the hob and its burner setting!

I'd look at that before running 28mm

 

[Last Plumber]

no one else seems to be asking this so.
does the size change from 22 to 15 at some point under the floor?
how much 15mm pipe is there?
that will starve the flow dramatically!

I've asked about the 15mm!

I also asked about the hob and its burner setting!

I'd look at that before running 28mm

 

[jaydebruyne]

I've asked about the 15mm!

I also asked about the hob and its burner setting!

I'd look at that before running 28mm

You mentioned before about getting rid of the 15mm to the boiler, which the floor needs to come up for. So if we gonna take up the floor might as well complete the run to the boiler in 28. At least if they add any other appliances they'll be covered.

The hob is old. But I reckon once the run is all 28 and I detest it it'll be alright. Anyway, we'll see.

I need to get a hold of some test nipples to cut into the pipe under the appliances

 

[Scott_D]

Are you getting paid extra or was it part of the job?

 

[Last Plumber]

Yes ok.

Getting rid of that 15 will make all the difference.

Vaillant loose a good 2-3mb through the tube to the gas valve.
Whatever your wp is at the valve, it will be 2-3 Mb above that at the pipe below the boiler.

 

[jaydebruyne]

Yes ok.

Getting rid of that 15 will make all the difference.

Vaillant loose a good 2-3mb through the tube to the gas valve.
Whatever your wp is at the valve, it will be 2-3 Mb above that at the pipe below the boiler.

I can't believe it loses so much - I'm really not a fan of Vaillant

 

[Last Plumber]

I can't believe it loses so much - I'm really not a fan of Vaillant

I think they're one of the best around tbh
There are a few that are similar to be fair
Been installing commercials and domestic for ages and had no real probs.

 

[jaydebruyne]

Ok.. so I've done the entire run now in 28, dropped to 15 about 20cm under the boiler - it tees off about 10cm to the hob in 15. Boiler still only getting 2.85 m3h when min is 2.9. Hob still going out on simmer but I'm gonna replace the hob anyway as it's nearly 30 years old. Also gonna buy a test nipple for the 15mm under the boiler. Could it not be that the boiler is only demanding 2.85m3h - as it's rating at 30kW gross

 

[ShaunCorbs]

Ok.. so I've done the entire run now in 28, dropped to 15 about 20cm under the boiler - it tees off about 10cm to the hob in 15. Boiler still only getting 2.85 m3h when min is 2.9. Hob still going out on simmer but I'm gonna replace the hob anyway as it's nearly 30 years old. Also gonna buy a test nipple for the 15mm under the boiler. Could it not be that the boiler is only demanding 2.85m3h - as it's rating at 30kW gross

so the boilers in 15mm?

and whats pressure at boiler when hob is on improved?

 

[newcastle phill]

Have you teed the hob off the 28mm ? And hob now ok ?

I haven't read the whole lot again. But your allowed 10% below and 5% above rated figures.
And what model was it

 

[jaydebruyne]

so the boilers in 15mm?

and whats pressure at boiler when hob is on improved?

The total 15mm run is 20cm but yeah boiler is in 15. Didn't test boiler once reconnected hob as tested boiler with hob disconnected and was still slightly low. It's peeing me off. But am getting 21.5mbar at meter working pressure and 16 at boiler inlet on valve. Need to buy a test nipple. It's a new run so can't be a blockage.