Cross posted from the home improvement board... there are three of us with similar issues and I'm hoping it might get more visibility here.

We bought our house 2 years ago and haven't had this issue until a water main just up the street from us ruptured in February. We were the first house down the line from it and had water coming up from under the sidewalk in front of our house as well.

Essentially, whenever we flip on all but 2 of the zones we hear water hammering in the wall that our master and guest bath share. It's the worst when the zones that feed the back yard are on, near non existent when the one feeding the front bushes is on. I'd say this wall is about half way between where the water heater is in the garage(rear of the house) and where the check valve is in the front yard. We have an expansion tank sitting above the water heater as well.

Would a suppression device on the irrigation line fix this? Maybe one on the water heater? I was of the impression that the expansion tank was supposed to prevent stuff like this but that could be inaccurate.

TIA

The expansion tank likely only controls the problem for the hot water line, the cold water lines still run freely across the house.
Does the irrigation system have a master valve? And what time of back flow device is being used on the irrigation: Doublecheck in the ground or PVB above ground?

What you've described sounds like air in the lines. Water hammer typically occurs when a valve is closed suddenly. Air in the lines will start making noise when the valve is opened. I had this issue with my sprinklers after not running them for a few months.

Solution - You have to get the water moving through the pipes quickly enough to purge the air. I manually opened 2 sprinkler zones (turned the valve by hand at the box in the ground) and then turned on an outside spigot close to the noise. The spigot ran for a second then sputtered with the air from the water line. I haven't had a problem since.

It sounds like your problem might be a bit more extensive than mine was, I only had 1 or 2 zones affected by the issue. It might take a couple of iterations to really clear the air in the lines.

I'm honestly not sure about the valve. It's a double check.

I tried something similar to this when it first started with no luck. I don't think I tried it with the water on(turned it off at the street) and tried to let the lines clear out. I'll give your method a go.

Opening more than one faucet with the water off would generally make the problem worse as the only way for water to leave the system without city pressure is for air to enter through the higher faucet.

The key to my suggestion is water velocity through your main supply lines. More open taps is better.

I figured I'd update this...

Plumber came out and said he couldn't find anything wrong inside the house or leading into the house. The fact that it only happened when the sprinkler system turned on suggested that it was an irrigation system issue.

Irrigation company came out and said we can install a suppression part, and that may work. Or, we can install an arrestor and that may work. Hard to tell without trying it. They just left after installing the suppression part and when the valve is fully closed(no pressure), the noise stops, which is shocking. The only problem is that the lines furthest away from the check valve don't have enough pressure to run. Open it back up, sprinklers run, hammering starts again.

Looks like we're on to the arrestor.

Check the pressure. I installed my sprinkler system and learned as i went. Had terrible, wall shaking, water hammer when it switched from station to station. Finally figured out that I had 90-100 psi on the system. Had to work with the city to fix it. Finally had to install a second meter to rectify it.

Meant GPM not PSI.

I would have to look back at my books but I think the optimum is 50-60 gpm of flow.

You can purchase a pressure relief valve from Home Depot for less than $50.00. Install between the backflow device and the tee to the main line to the house. This way you can regulate the irrigation system pressure separately from the house without having to go through the expense of another meter.

OP what is the water pressure at your house?

If you have a Rachio controller then there is an option to reduce water hammer. It slowly turns the valve on and off versus all at once. Check your controller for a similar option.

Apache said:

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You can purchase a pressure relief valve from Home Depot for less than $50.00. Install between the backflow device and the tee to the main line to the house. This way you can regulate the irrigation system pressure separately from the house without having to go through the expense of another meter.

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Yep, but it made more sense to install a separate meter because I was paying sewage off the house meter for the yard watering. A few $6-700 water bills made it a no brainer.

I checked the front hose tap the other day and it was about 90psi.

Is there an easy way to figure out where to place the valve? Our street hook up and the double check are in very odd places based on what seems logical to me.

I have ongoing problems with water pressure from San Antonio Water System. Pressure delivered to our house is 140 psi. It has knocked out 3 pressure reducing valves in the last ten years. We are currently on our 4th PRV. It's a heavy duty model and currently holding at 85 psi. Get a pressure gauge from Home Depot or Lowe's and check the pressure at hose bibb

Have an accumulator that drained during the outage?

Sorry I missed this topic OP.

There is a great DIY sprinkler system maintenance resource that came in very handy a number of times for me called IrrigationTutorials.com

It has a article specifically On Water Hammer

https://www.irrigationtutorials.com/waterhammer.htm