High pressure spikes in domestic water.

[TCP]

Hey members, so after installing a PRV I noticed I'm getting huge spikes of pressure whenever a toliet flushes or washing machine runs and stops BEFORE my PRV. I probably was getting these spikes before but now I have the gauge to see them. So with my install I put gauges before and after my prv. Pressure coming from the street is around 80-90 psi. With the spikes it's can hit 170 or more but only before the valve. The pressure after is fine and does not move at 50 psi. My question is is this bad for prv valve and also what can be done to fix this.
So on the street pressure side I have my irrigation system so it is feeling these spikes too. I installed a 3/4 water hammer arrestor on a tee near the irrigation branch. Also on a hose spigot at the house I put a mini shocktrol which has reduced the spikes down to 95-100. But the mini shocktrol needs to be refilled about every other week or it loses enough air to make the water bounce when the spikes happen.
So with winter coming I want to cut in a tee on the supply line and install a ball valve with drain. This way I can isolate and remove pressure before repumping air in the trol. My question is would an air chamber be much easier to drain and reset? Or is there another idea that would be better all together.

 

[Jadnashua]

There are numerous reasons why a supply pressure could spike. What you might be seeing is the result of an undersized supply line that has high velocity that tries to stop when the load stops...inertia wins. A hammer arrestor might help. AN air column won't stay an air column very long...that air will get absorbed by the water, and eventually, will be filled with totally water and stop working. An engineered one should last many years. They work best when installed as close as possible to the valve or blocking point.

 

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[TCP]

Hmm the only reason I suggested the air chamber was because I was going to install a ball valve with the tiny drain hole attached to it. So every now and then I could close the valve and drain the water. The shocktrol is a pain to pump up and I think I'm pumping it to the max. Also worried if it does fail will it flood my boiler room or throw debris down the line into the prv. Most of the engineered ones I found have less max pressure or are sealed and can't be charged more so they didn't do much since the supplied pressure is so high.

 

[Jadnashua]

There are two general types of engineered hammer arrestors:
- those with a sealed chamber and a sliding piston
- those with a bladder.

Those with a bladder may have an air valve that can be used to adjust it. When one of those fails, they don't tend to leak, they just stop functioning until they rust out from the inside. The reason they work long-term is that the trapped air does not come into contact with the water, which will absorb some, eventually, purging all of the air out of the thing and making them useless. It's not always reliable to try to empty an air column of water...think finger over the end of a straw full of water...it doesn't always drain.

I've not looked, but they probably do make these in industrial sizes, mean for higher water pressures.

 

[Reach4]

Therm-X-Trol tanks are rated for 150 PSI maximum working pressure. Maybe set the air precharge to 90 PSI.