Reducing Tee & Return Flow Restriction

[Careful_Bodger]

I was planning to replace like with like on a scaled-up feed/vent assembly (close-coupled, 3" between them, 6" from the pump), but I notice that the new reducing tee for the 15mm feed has a small but significant reduction in the thru 22mm bore. Is this normal, or have I purchased the wrong type of tee.

I could use a 22/22/22 tee, and then use a reducing 22/15 coupler for compatibility with existing pipework. Any comment? The vent is all 22mm back to the header tank

What is recommended practice, dimensions, spacings for close-coupled feed/vent pipework?

Thanks for all your useful comments

 

[ChrisR]

What you have sounds fine for spacings. Know what you mean about hte reduction - some of them seem to be 5mm thick copper in the middle!

What you can usefully do is take the feed down past the flow pipe, and join into it from below. That stops convection currents taking water up the feed pipe. It may even help stop a repeat of the scaling. It seems to be an unaccountably fussy part of a CH system, so I'd use your suggestion of the 22mm equal tee and reducer.


Just noticed your title is a bit confusing so I'll spell it out

Boiler flow then vent vertical 22mm as soon as possible (mine's 6 ft sideways) then feed asap (though 6" is often quoted for some reason) then pump which should NOT be pumping downwards then auto bypass then valves.

 

[Careful_Bodger]

Thanks ChrisR,

Sorry about the confusing title - I have a back boiler (B. Baxi) with a vertical pipe run into my loft (bungalow!), a couple of bends - so that the vent/feed/pump run is arranged horizontally - with a 22mm vent (at about 30deg from horizontal), then after 3" a 15mm feed (again ~30deg from horizontal), then the pump, then mid-position valve, HW tank, etc.

This means the vent is about 10' of pipe run from the boiler. Is this okay?

I was planning to keep this general arrangement unless I am told it is wrong.

The restriction due to the 15mm tee would therefore be in the return to the pump, after the 22mm vent, and might (to my way of thinking) encourage pump over.