Reducing 22mm to 15mm on central heating trunk.

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Hi guys can anyone tell me if there is optimum position/layout to place a 22mm to 15mm reducer on the central heating circuit. Is it better to use a T at this point for more than just ease? ie flow. Should the 22mm feed be longer than the return? Is it best to reduce after the last branch to second to last radiator? Hope this al lmakes sense. thanks in advance.
 
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Don't really follow you well here... 22mm pipe will give better flow rates than 15mm but it all depends on the size of your system as to what is required.

As a basic rule of thumb the largest diameter should be nearest the boiler then taper down as you get to the last rad. Same on the return.
 
Sorry your missing my point my fault im not explaining it very well. I have 22mm round most of the house the last two rads (not getting very hot) are on 15mm the redcucers are on straight runs of pipe. Would they be better on Ts. Ie at the third to last rad 22mm down to 15mm on the branch and to 15mm on the trunk. Or will this not make any difference.
 
Sorry, I'm not quite getting it. What do you mean by trunk? Also, not sure how you can replace a reducer with a tee being a different fitting.

A system with a mix of 22/15mm should work spot on with a bit of balancing, have you tried that?

Maybe draw a diagram and post it up.
 
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heres what i mean by branch and trunk this is off wikipedia.
my set up is slightly different the last TWO rads are on 15mm :
the whole system is fine apart from these the last two rads.
 
Ah, trunk is probably American terminology then.

There's nothing wrong with the second picture, the system will just need balancing. Do a search for balancing radiators.
 
Spot on Andy, i thought they had been balanced but on inspection the valves were fully open. I suppose the flow was far too fast through them. Thanks for your help and all the best.
 
Prime example of overthinking!

The simple causes are usually the answer.

Thats why women are so good at boiler repairs!

Tony
 

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