3/4 Brass coupling with nylon thread, why?

[Plumb Duff]

Hi all, I recently got with a pressurised water heater connections consisting of 3/4 brass nipples and brass couplings, the coupling has rubber seals and nylon internal thread, why would this be the case and can I not just directly couple to the water heater without the coupling supplied using 3/4 elbows to the water heater with the nipples fitted? What is the purpose of the supplied coupling? (attached photo)

 

[SimonG]

So you dont damage the heater by riving on the fittings.

 

[JCplumb]

They're dielectric couplings, they help prevent corrosion in the heater.
If you don't fit them your warranty will be worthless.

 

[Plumb Duff]

I should perhaps clarify it is the nipple that is designed to first connect to the water heater then the coupling into that, if I can connect direct to the nipple with an elbow (and this would be the preferred way due to space constraints) then I don’t need the brass/nylon coupling?

In reply to SimonG (thank you) surely the heater protected from damage by the nipple? Correct me if I'm wrong.

 

[stani]

Jcplumb is absolutely correct and the warranty is worthless without them.

 

[Plumb Duff]

JC yes that sort of makes sense to me as it looked like it was designed for electrical isolation (albeit water is a conductor) having said that I'm using PVC covered aluminium pipe and it would suite a lot better if I could use the supplied coupling a couple of metres from the tank as opposed to directly onto it, would it make any difference... in your opinion?

 

[stani]

It's not for electrical insulation it's to stop corrosion caused by dissimilar metals.

 

[stani]

https://en.m.wikipedia.org/wiki/Galvanic_corrosion

 

[Plumb Duff]

Advise duly taken they will be fitted, many thanks to all that replied

 

[ShaunCorbs]

To be fair them ones look decent ones, normally there a bit of formed plastic just normally bin them as the tails out the heaters are plastic any way :s so no need and they always break/ snap as they can't take the heat and cooling

Ariston water heaters

also are you G3 registered as any pressurised water heater needs to be installed by a G3 qualified person