New 3 port valve change query and pipe size KW loading Q.

27 Jun 2009
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United Kingdom

I have a query please that I'd like to possibly ask: I am changing my old Drayton 3 port valve (mid position type) for a new modern Honeywell V4073A type. I believe these are the most popular types and the best to have.

Basically, I know the wiring colours (I have a chart/book that says the slight variations for motorised valves). My query is this: The valve has been there years and years, and probably before metric came in. So when I remove the valve after draining down, will the new 22mm nuts/olives fit OK and seal Ok on the old 3/4" pipes? Or will I have to do something to make them fit such as re-pipe??

If anyone can help me I'd be really greatful.

One other query I'd like to mention whilst on-line, is the following: It is pretty random but - in a plumbing/heating book I have it says that 15mm pipe has an approx. loading of 6kw and 22mm pipe has an approx loading of 13kw. My boiler is 28KW and the pipes from it are in 22mm and tee's off up to the rads in 15mm pipe. So is my system OK/efficient?? I know it is a random question, but it just puzzled me! Is the book wrong or what exactly does it mean please??

Thank you all for reading my post,

Best wishes

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Provided the olives have not damaged the pipe, you can cut the olives, clean the pipe and stick the new valve on if it does not fit as is.

The pipe question is easy; if you have no heating problems, the 22mm pipes are adequate.
as bengas says should be fine but you can get 3/4 olives so just replace the 22mm ones if you have problems

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