Hi, I bought a house last (built 1988) which had a 3 port valve (Honeywell V4073A), a vented cylinder and 2x tanks in the loft. I had a plumbing company remove the cylinder, 2x tanks and replace it with an pressurised cylinder and filling loop along with new radiators. They chose to keep the existing 3 port valve. That company never actually came back and finished off so I had to get the plumbing company who did my bathrooms to commission and fire up the system. I asked them to check the work done and they never commented on the valve being incorrect. I've now chosen to have a Honeywell Evohome installed and the person who I found on the Honeywell approved installers list came out and said my value should have been changed to a 2 port valve for safety reasons. He said a 2 port valve is actually supplied with the new cylinder and my first plumber should have fit it. He's given me a quote to install the Evohome but also to supply and fit a new 2 port valve. Can somebody please help me on which is correct? Thanks.