odd plumbing noise

Sometimes when we are running two faucets/etc at once, the pipe into the house starts making a noise very much like a train (chugchugchug). Then the water will come in spurts.

Any idea?

In the common faucet, the valve is not moved up and down by the spindle.

It is only moved up by the spindle , it is not held DOWN by the spindle.

This is not normally a problem as the water pressure will push the valve to closed… as far closed as the spindle lets it.

However, the valve can become forced by reverse pressure to open up FURTHER than the spindle. Then when the pulse of reverse pressure eases, the faucet flows at full speed for a bit, until the flow rams the valve home (as far as the spindle lets it.) … and the sudden alteration of flow rate causes hammerring in the pipes. (the pipes giggle around… )
The other faucet gets the opposite effect, and they keep causing hammering which opens them both up … which causes hammering (both on the radical fast turn of full rate flow, and the radical slow down as the valve rams home again), , which causes them to open up…

A common cause is loose pipes… pipes that jiggle around … someone turns a faucets handle faster than is sensible with the sensitive pipes, and they jiggle and cause pulses in the pipes… hammering … the pipes can be secured down, with clamps,screws, bent over nails, and so on, or you can install anti-hammer devices.

Thanks. Not something I need a plumber for? Will it get worse or cause damage?