I had a new hot water heater installed, and shortly after that, it
would discharge water. The plumber who installed it, said that the
pressure was too high likely in the house. He looked at the pressure
reducer value which he said was old and broken. So he replaced it. He
also claimed this would stop the water spike we got in the house. I'm
defining a water spike, that at random times during the day or night,
when you turn on any facet water will blast out for about 10 seconds
and then return to a normal flow. I have not been able to see a pattern
for this. I have seen it do this within minutes after using the shower
and then getting a drink a water from the kitchen sink.

The plumber, who by the way has a master plumber's licenses was
surprised that we still had the water spike problem. Assuming that the
new unit might be defective, he replaced it with one that was assemble
in the US instead of China, thinking that perhaps the charge in product
might have caused the problem.

This didn't solved the problem, still several times a day, without
warning water comes blasting out. The plumber said he didn't know what
to do, since he didn't think it was likely that both of these pressure
reducer valves were defective. I asked if perhaps the ones he was
installing simply were robust enough to handle the high pressure and he
said that this is a very normal device he has been installing in my
area for many years and never had a problem.

This led us to talk with the local water company. Maybe the pressure
coming in from the street was so great that this device couldn't handle
it when it would spike. After many phone calls I finally got the water
company to return my call and be interested in the problem. The last
call, I gave him the phone number of my plumber since he was most
familiar and understood the system. After all, I'm just a home owner
and don't know much about this stuff. I got a phone call back from the
water company and said he talked with my plumber and after discussing
the problem the plumber agreed with the water company that we should
install an expansion tank over the hot water heater. I explained that
the water spikes come from the hot water and the cold water as well.
How is an expansion tank over the hot water heater going to solve the
cold water spikes too I guess, and he said he didn't know. He said the
plumber will be contacting me.

I talked to the plumber and he said that about in 25% of the homes that
they install new hot water heaters, they need expansion tanks, and that
this affects the hot and cold water as well. While I am waiting for a
quote to have this expansion tank installed, I thought I would post and
ask if others have had this experience or could shed some light on it.
Does an expansion tank sound like the solution?