Vaillant UNISTOR unvented, tundish dribble

[ShaunCorbs]

Yea double check should sort it you could use a swing valve

 

[Ted808]

Yea double check should sort it you could use a swing valve

SWING VALVE?

 

[ShaunCorbs]

What is a swing check valve? - AVK International

 

[Ted808]

What is a swing check valve? - AVK International

I see! Non in 22mm that I can find.

 

[ShaunCorbs]

Water Swing Check Valve - Brass 3/4" BSP 7463 | BES.co.uk

 

[Ted808]

Water Swing Check Valve - Brass 3/4" BSP 7463 | BES.co.uk

Do you think this type of valve will help with this?
the fact is that now the check valve makes the hot water pipe groan somewhere, I think it's the vibration through the seating on the double check valve-
I wish I'd not gone down this road-live and never learn!!