I discovered why the water pressure in my fire prinkler system kept rising. It's because the hot water pipe is right up against the sprinkler pipe causing it to heat which then increases the pressure. Now can I wrap the pipe with insulation. Would this be a good fix? If so, should I wrap the hot water pipe or the sprinkler pipe to keep it cool? The house is 13 yrs old. Have the pipes started to sink down or what?

If you have room put a piece of insulation on each one of the pipes. And yes the house may have settled a little over the years.

Go down to your local plumbing shop and pick up some Armo-Flex Insulation. Insulate both pipes. Good luck, tom

If it's a single hot water pipe touching the sprinkler pipe, I don't really think that's your problem. There's not enough heat transfer there to change your water pressure in your sprinkler system. What I think you're seeing is a surge from the city water system. Happens all the time. BTW, I install fire sprinkler systems.

If soundman's correct then a PRV(pressure regulator valve) would solve the problem. Good luck, Tom

I install Fire Sprinkler Systems for a living as well and agree. That would not be enough to cause the rise. Typically the rise would be from extreme changes in air temperature or a boost from the city pressure over night. Typically surges will happen over night and push more pressure into the system. You probably have a backflow, or check valve on the system that keeps the pressure in. I test all my sprinkler systems at 210 lbs pressure for all my inspections, so the pipes are capable of holding that type of pressure. Is there a drain valve you can crack open slowly to drain the pressure? If so do that before you go to sleep if the pressure is back up high in the morning it may be surges. Do this again in the morning and check later in the afternoon.

By the way if you have alarms wired to the system do not open or close any valves without notifying the alarm companies and local authorities. You don't want to set off a flow switch or Tamper alarm. You may want to insulate those to pipes touching anyway, so the copper does rot away.