Shower pressure drop if from direct 22mm pipe to combi still on 22mm dia?

[bgates]

Shower pressure drop if from direct to combi?

Summary:

Ie if I get rid of the existing indirect system (22mm pipes) , and replace it with a combi that is feeds the shower on 15mm for 3m, then 22mm for the final 3m from the existing indirect system, how is it likely to perform (ie pressure or flow rate wise relatively speaking?)

Detail:

We’ve inherited a modified system: indirect, unvented 150 liter valient boiler, fed by a gravity tank, boosted by a faulty pump. There is also an expension tank fitted, and a separate sort of feeder boiler. It feeds one bathrooms which has a shower, and an ensuite which has a bath and mixer tap.
The pipework to the showers are 22mm dia.

There is a 3bar mains feed.

If we change the feeder boiler to a combi boiler (to make space in the main 150litre boiler cupboard, and provide an unlimited supply for long showers – otherwise were limited to the 150litre tank) how can I work out , or guage in advance how the combi would perform if we didn’t change the pipework from the existing 22mm dia , to new 15mm (rip out the whole bathroom!) option.

Many thanks.

 

[bgates]

I don't think I was clear enough before and would be really grateful for some help.

Can I run a shower from a combi boiler via 3m of new 15mm pipe that goes to 3m of existing 22mm dia pipe?

The existing 22mm is from an indirect system that we want to get rid of to make space.

I’ve been told that we’d need to change the rip out all the tiles etc to replace the 22mm with 15mm

We would be running 2 showers from the combi (though only very rarely would this be at the same time). Could maybe put an electric shower in 1 of the two bathrooms.

Many thanks

 

[AWheating]

its best to remove as much of the 22mm on the hot as possible, but it will work with the 22mm left in. If you have two showers one being electric is a good call..... if boiler breaks down you still have one shower.

 

[bgates]

many thanks.