:- I have no hot water... the water makes it to the bottom of the immersion tank as I can feel pipes are warm.. but no hot water from gas bolier... only if use imersion heater! Help!

Hey Matt, I'd like to help you out but I'm a Florida plumber and we heat with heat strips aqnd reverse air down here. I've never worked on home heating systems. Since it appears that I'm the only plumber working this page, let me direct you to another free Q&A site where I'm sure your question can be answered. AllExperts.com has more plumbing experts and I'm sure they can take care of you. Again, sorry I couldn't be more helpful. Regards, Tom