Advice - 15mm gate valve to 22mm flow

[Ccw1971]

Hi, new member here, so hello! I recently bought a house that needs heaps of work, so have no money and lots to learn along the way.
Ive had a new WB 8000 Life 40kw system boiler installed on my gravity fed system. The house is a long bungalow with roof rooms which had no heating so I asked my plumber to put a couple of T gate valves on the flow and return just after the pump and motorised valve (which sit at the same height as the upstairs floor) to allow me to run pipe (aprox 12 meters each way) for 3 rads. Im doing it in plastic, have fitted the rads and bought all the supplies (which I cannot return) to do 22mm flow and return with 15mm to the rads. Unfortunately I've now just noticed the T gate valves the plumber fitted are reducing from 22mm down to 15mm. Will this cause any potential problems as I cant return the supplies, so plan on going ahead as before but just going back up to 22mm from the gate valves. Or should I drain down and have the gate valves replaced to 22mm equal Ts, which is more work and expense? Thanks for any advice.

 

[ShaunCorbs]

What size / output are the rads ?

 

[Ccw1971]

They're Stelrad Vita K2 600 x 1000, so 5500btu each.

 

[ShaunCorbs]

I would change it to 22mm as your port valve is that size does the return reduce down or is it a tee off ?

 

[Ccw1971]

Both the gate valves on the existing 22mm flow and return are reducer Ts going down to 15mm. The new circuit would connect into these. The new circuit F&R to the 3 new rads from the exitsing F&R (serving the rest of the house) would look like this... 22mm(existing flow), 15mm T off (reducer gate valve), back up to 22 (new flow), 15mm to rad and back, 22mm (new return), 15mm at T(reducer gate valve), 22 existing return. Hope that makes sense.
Would reducing down to 15mm through gate valve cause any undue restriction. I already have all the 22mm pipe and fittings, so I'd like to use them. Would it be necessary to swap out the 22/15 gate valve Ts.

 

[ShaunCorbs]

Yes best to swap it all to 22mm

 

[Ccw1971]

Thanks for that. Other than keeping it 22mm is of course the correct way if doing it! What would be the negatives if the reducer Ts were left in place?

 

[ShaunCorbs]

Your limiting your flow so it could reduce your heat capacity

 

[Ccw1971]

Id like to get the upstairs radiators running asap, so short term, the only issue I could face is possible less efficient heating of these radiators? Can you just confirm that. If so, I'll crack on and save swopping out the gate valves for 22mm till the spring. Thanks.

 

[ShaunCorbs]

Two will work the 3rd might not

 

[Ccw1971]

Two will work the 3rd might not

Is that due to going from the 15mm T up to the new 22mm new flow and return. Would it make a difference if it was all run in 15mm from the T off of the existing 22mm flow and return? Is it not possible to T off a 15mm circuit from an existing 22mm?

 

[ShaunCorbs]

Yes it’s like having a valve half shut

 

[Ccw1971]

Thank you