Having a check valve installed this afternoon!

Shindig:

 

This happens when the washing machine is running, I'll be outside near the vicinity of the Rheem 27 and would hear the unit spark up and then stop. 

 

Thanks for the replies, going to sort this bug bear out as it's a waste IMO. 

 

Also, I was tempted to remove the hot water pipe to the washing machine. I made sure when purchasing the unit I bought a model that heated the water up itself as I had read it was more efficient to do so. 

 

Thank you

 

The water solenoids on F&P front loaders snap shut like bear traps. I expect they send shockwaves through the pipes and if you have any old PB pipes they're at risk of cracking and leaking.