Need to know a little more detail here before I can help you properly.
1. The Valaint water heater is it set up for Natural or LPG Gas currently?
2. Is it an internal or external model?
3. If it is an internal model does it have a flue connection on the top of it?
4. It will also depend on what water pressure the water diaphram valve assembly is set up for as some are for low pressure water and most are for mains pressure – they are not interchangeable without buying a complete water valve asembly to suit.
5. Where is your currect location?
I look forward to hearing more from you.
Selgas Services Ltd
Craftsman Gasfitters, Plumbers, Electrical Service Technicians