Could flushing fire hydrant repeatedly burst main in front of house?

[Davej]

The water department keeps having to dig up and replace main in front of my house - 2016, 2020, 2022. Its very disruptive as it means replacing concrete curb on the street, driveway apron, repaving large sections of the street, re-doing my tree lawn irrigation system, re-seeding tree lawn, etc. My tree lawn still isn't right from last time in 2020.

I have pictures and dates of all the repairs, and noticed they are oddly the SAME DAY for each break! I thought how could this be when my wife mentioned the bursts are in the vicinity of our fire hydrant, and fire department just did their flush tests. So I looked through my old text messages from the city and it seems they always test my hydrant around this time of year.

Could fire department doing annual hydrant flushing cause the water main to burst a couple days later? As an additional point of information, I did have a PRV and an expansion tank installed because during the home inspection my water pressure was 95 psi.

 

[Terry]

Most water departments will flush hydrants on a routine basis just to make sure they are usable when needed. The flushing shouldn't be an issue for the pipes in the ground. I wonder if they are opening and closing them too quickly and having hammer in the line? 95 PSI is considered a high pressure.

 

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[John Gayewski]

I suspect the same as Terry. If they are causing water hammer then yes they could be causing lines to break underground. Most municipalities receive training on how to avoid this, but with high pressure like that there are sometimes some piping solutions that should be done underground to divert the shock of water hammer. It's possible they don't know or don't have the proper engineering for water pressure that high.

 

[Valveman]

There are two ways flushing a fire hydrant can cause lines to break. One is if they open the valve all the way, the velocity of the water rumbling down the line can be damaging. But usually the main lines are large enough to prevent high velocity damage even at high flow. The other way lines can break is by opening or closing the hydrant too fast. Opening too fast can cause negative pressures which are followed by a shock when the water catches up. Closing too fast can cause the pressure to build up quickly. Think dropping a boulder in front of a moving train. A big valve on a main line should be opened and closed very slowly like 10 minutes to open and 10 to close.

 

[WorthFlorida]

If you're in an old development with an old water distribution system, the pipes are weaker due to many reasons, notably corrosion. What is probably breaking is where the repaired section of new pipe joins the old pipe and the old pipe gives away. By chance is your home at a lower elevation where the water flows downhill? When the water flow is stopped too fast, pressure plus gravity is building pressure.

 

[Storm rider]

This was a pretty chronic problem where I live. Every year when they tested the hydrants we could count on several leaks in the system over the next week or so. The county replaced all the mains and hydrants two years ago and so far we haven't had any more leaks.

 

[Davej]

If you're in an old development with an old water distribution system, the pipes are weaker due to many reasons, notably corrosion. What is probably breaking is where the repaired section of new pipe joins the old pipe and the old pipe gives away. By chance is your home at a lower elevation where the water flows downhill? When the water flow is stopped too fast, pressure plus gravity is building pressure.

Yes, its a hilly area and my home is in a bowl - and the house is like halfway up that bowl. The main is in the street at the bottom of the bowl.

 

[Jeff H Young]

Its the straw that broke the camels back. is it because its in poor condition? or because they did thier job wrong? 100 years old and already leaking and now it blew completely out what is the cause? a good question