We have recently had water hammer issues. Plumbers have installed an arrestor near our kitchen sink and a device in the toilet cistern to slow water shut off. Worked for a bit, but hammer returned. This morning, while the toilet was refilling and the shower was on, there was a loud thud that came from the toilet/bathroom sink area, and all of the water suddenly shut off (from the entire house). Water pressure would slowly return, but would only last a few seconds before it would drop out again. I turned the main valve off (under kitchen sink) and turned on some taps. Eventually found out that the pressure had returned to normal. Cannot replicate what happened. And the water hammer seems to have disappeared. Hoping to see if anyone knows what just happened, and how to keep it from happening again. Thanks.