I have a 3" pvc underground water line serving a commercial property. It's 40gauage and 200psi. We have had several breaks in the line recently and have been told that it might be pressure spikes? How likely is this and what is a sign that it could be pressure spikes?

You might get a few different answers to your question since we cannot see the damage because no pictures are posted.

Is the break at a coupling or other device or is it in the pipe itself?

If it is in the pipe itself is the break complete or does it just create a hole?

Is the hole smooth or jagged?

What is the normal operating pressure of the water being supplied by the pipe?

Do you have a main pressure reducer before the pipe or does it take strait street pressure?

Is there a known pressure problem with the supply of water from the source. IE high pressure spikes.

Was the pipe installed properly as per the local code and the pipe manufactures recommendations? IE proper bedding and encapsulation by approved fill materials.

If the pipe is a long run were allowances made for proper expansion and contraction? This might have been done on long runs where different offsets are made during the install.

Are there any main valves like used on commercial sprinklers located in the outside pit or inside on the sprinkler tree? Does the fire department test the sprinkler system if so equipped?

Is PVC pipe really approved for use in your area? In my area PVC cannot be used for a water supply line.

Just trying to get more info so myself or others can possibly make a informed decission. Speed Ball will probably have a better idea than me on this subject.

You want to make sure you have the proper density PVC line for your application. There should be a stamp on the pipe telling you how much pressure this particular pipe handles. Look it up . Than subtract 20%. That's your maximum pressure this pipe should carry.

PVC pipes that handle different amounts of pressure look identical and cannot be distinguished by just looking at them. We always use the one that handles up to 470 psi. That way, we are sure the pipe will handle all the pressure w/o pressure-related leaks.

So, if you have pipe that carries 178 psi, you will have leaks... If you have pipe that carries over 400 psi you won't have pressure-related leaks..

Places like Home Depot don't put too much importance on advertising what kind of pipe the have in stock. With every shipment, they may carry pipe that carries different pressure. It is up to you to read the print on the pipe that specifies this important information.

Pvc under ground, in my area must be at least schedule 80, with high pressure fittings. Pvc is not allowed inside the house for water supply, only cpvc(which in my opinion is worse.) If you only have schedule 40 pvc for you underground supply, I believe you may keep having problems. Interested to hear how things work out.