I changed the thermostatic valve on a radiator in my bathroom and since then i have had no hot water. I have a primatic hot water tank in the attic and it just refuses to heat up. I have a back boiler which ignites but i do not get any flames, and it switches off after 10 or seconds, but when the central heating is on the radiators work better then they ever have done before, the ignition lights up on the back boiler and i get the flames. I drained the system via a drainage valve on the downstairs radiator as this is all i have, i also turned off all the hot water and central heating before proceeding, i have bled all the radiators and this still hasn't fixed the problem. Can anyone offer any help as i have three kids who need a bath !!!