15mm from combi to 22mm?

[estorilblu]

Hi Everyone i have read so many post with the same issue and still dont know what to do i have just had a new vaillant combi 937 fitted and am doing a new bathroom my old boiler was system fed and cold tank.
My question is the boiler has 15mm hot outlet should i go up to 22mm into the bath room and bath then 15mm to thermostatic shower and sink toilet? or stay all the way at 15mm then 22mm just at bath? also what size for cold please advise i have access to everything so would like to get it right first time. what is the best as its confusing with flow and pressure bathroom is very close to boiler thanks for any advise Merry christmas

 

[danplumb]

just take 15mm to the bath hot and cold, and shower, it will be fine.

 

[Agile]

Your boiler is capable of a good DHW flow rate.

15 mm from the boiler to each outlet is fine.

However, depending on the distances involved its often useful to use a 22mm cold supply to the boiler to obtain the maximum DHW flow rate.

Changing stopcocks to full bore lever valves can also help.

Did anyone bother to measure the dynamic flow rate available from the mains?

Tony

 

[estorilblu]

Your boiler is capable of a good DHW flow rate.

15 mm from the boiler to each outlet is fine.

However, depending on the distances involved its often useful to use a 22mm cold supply to the boiler to obtain the maximum DHW flow rate.

Changing stopcocks to full bore lever valves can also help.

Did anyone bother to measure the dynamic flow rate available from the mains?

Tony

Has only been measured at tap 20 ltr min so maybe more from the main stop cock yes has 22mm all the way to boiler then reduces to 15.

 

[ChrisR]

Most taps will limit to 20l/min but it has to be a pretty good supply to get 20.
Try with all mains taps open and everythingn running - eg outside taps, cisterns refilling if there are any... If the flow sticks at 20 l/min you're probably fine.

After the boiler stick to 15mm.

 

[BHP]

Hi Everyone i have read so many post with the same issue and still dont know what to do i have just had a new vaillant combi 937 fitted and am doing a new bathroom my old boiler was system fed and cold tank.
My question is the boiler has 15mm hot outlet should i go up to 22mm into the bath room and bath then 15mm to thermostatic shower and sink toilet? or stay all the way at 15mm then 22mm just at bath? also what size for cold please advise i have access to everything so would like to get it right first time. what is the best as its confusing with flow and pressure bathroom is very close to boiler thanks for any advise Merry christmas

First thing to do is to check your incoming mains supply flow rate by running your kitchen sink tap for 1 min this will give you flow rate l/min next step would be to check hot water flow rate. If flow rate is OK then you can supply your bath room with 15mm copper also you can fit isolation valves to your appliances with flow restrictors in them BES have them also Screw fix flow rate are 6l 9l 10l or 12l that is l per minute BHP