Need Gledhill immersion heater rather than standard?

Hi,
I need to replace the immersion heaters on a Pulsacoil III - so this means 2 off Gledhill XB078 at around £60. Is it actually necessary to use Gledhill parts? For example I can find a generic 11" 'long life' immersion heater and thermostat for around £15. However, I'd rather not find out that the Gledhill units are special and necessary after I have drained the system down. Any information would be much appreciated.

It's always best to use Gledhill parts but nothing stopping you not! Gledhill genuine parts do tend to last longer.

I find that the generic heaters fit ok but use 20 turns of ptfe tap on the thread as the seals are not so good.

Heaters but be made of an alloy called Incoloy, these are available most places.

Draining tip: If you can remove the MT cock and fit a 1/2" adaptor and gate valve with a tube and cap in the open end, this enables fast draining, also have a wet and dry vac ready when using the MT cock, water escapes everywhere.
Tip: Rap ptfe tape on the spout of the mt cock to get a tight fit to the drain hose especially if draining over the side of a bath. A syphon canbe helpful and will not establish with air leaks at the mt cock.
Paul.