What would be causing this to constantly crack?

[Btz]

When we slowly let the water into the tank the plumbing instantly cracks in the same place where comes into the bypass valve. The resin tank is empty. This is the second time it has cracked in the same place.

 

[Chucky_ott]

Are the threads for those fittings tapered? If so, I'm guessing you are over torquing the female fitting. The more torque you apply to a tapered pipe thread, the higher the stress on female fittings. As to why it's cracking when you turn on the water, I have no clue.

 

[Sponsor]

 

[John Gayewski]

Lateral stress. Someone is bumping it or it's getting torqued.

 

[GReynolds929]

Because it is a plastic female adapter. It should be a metal female adapter. Plastic will crack, especially if over tightened, which is very easy to do.