County Water Pressure Too High

[Valveman]

"If you are 1' below the highest level of water in the tower you will have .43 PSI. If you are 10' below you will have 4.3 PSI. A hundred feet will give you 43.3 psi and down the line."

Amazing, had one of the dozen of utility employees I have spoken with had given me the simple explanation of the pressure being a result of gravity not pumps I would not have been bothering them. Unfortunately they most likely do not know themselves.

I have lived in the house for 15 years, initially pressure was around 75psi, based on my new found knowledge, I guess the increase occurred when they built a new water tower a few years back. I like high water pressure, if I don't feel sand-blasted after a shower I'm disappointed. Recent events including the main line that supplies water for the whole community busting 3 times this year and more time on my hands made me decide to try and find a resolution.

It will be easy enough to install a regulator however I also wanted to replace the thin walled pvc off the meter the knuckle-headed builder installed which makes it a much bigger project. Always amazes me what contractors will do to save a few dollars.

Thanks for all the great information!

Gravity from the upper level of a water tower is what determines the static pressure in a system. But the pump or pump(s) still have to produce that much pressure, as the water doesn't magically appear in the water tower. When the pump(s) start there is usually a tremendous pressure surge in the line, and then the pressure is usually considerably higher until the tower is full and the pump turns off. When the pump turns off there is usually another surge of pressure as the check valve(s) slam and bounce the pressure back to the system. Only when the supply pumps are off and the transient pressure waves have died down will you finally see the static pressure from the tower(s).

A pressure reducing valve and an expansion tank will take care of the surges on the house side. But the public water supply people will have to figure out how to eliminate water hammer from the pumps cycling on and off to stop breaking the mains. Pumps cycling on and off to fill water towers is one of the biggest causes of water hammer and main line breaks.

A 1" PRV will probably be fine, but you don't want to oversize a PRV very much. While a PRV that is too small can restrict the flow and pressure when you are using a lot of water, a PRV that is too large is not open very much (not working in it's sweet spot) when you are using very little water. This will lead to wearing off the seat in the valve and letting it leak high pressure through again.
PRV1A Pressure Reducing/Regulating Valve – Cycle Stop Valves, Inc

 

[Deere Dude]

Gravity from the upper level of a water tower is what determines the static pressure in a system. But the pump or pump(s) still have to produce that much pressure, as the water doesn't magically appear in the water tower. When the pump(s) start there is usually a tremendous pressure surge in the line, and then the pressure is usually considerably higher until the tower is full and the pump turns off. When the pump turns off there is usually another surge of pressure as the check valve(s) slam and bounce the pressure back to the system. Only when the supply pumps are off and the transient pressure waves have died down will you finally see the static pressure from the tower(s).

A pressure reducing valve and an expansion tank will take care of the surges on the house side. But the public water supply people will have to figure out how to eliminate water hammer from the pumps cycling on and off to stop breaking the mains. Pumps cycling on and off to fill water towers is one of the biggest causes of water hammer and main line breaks.

A 1" PRV will probably be fine, but you don't want to oversize a PRV very much. While a PRV that is too small can restrict the flow and pressure when you are using a lot of water, a PRV that is too large is not open very much (not working in it's sweet spot) when you are using very little water. This will lead to wearing off the seat in the valve and letting it leak high pressure through again.
PRV1A Pressure Reducing/Regulating Valve Cycle Stop Valves, Inc

From what I understand, although some plans may deviate, but the water just flows from the tank by gravity to your house.

The city well pumps have a separate pipe running into the top of the inside of the tank and doesn't cause surges to a house. It is separate from the pipe going to the houses and it just tops off the tank to whatever the float level decides. If the pumps start it may cause a little turbulence when water splashes out of the pump tube, but not enough for any concern and wouldn't have any noticeable effect in a home. Just check some images googling, "How water tanks work."

 

[JRobyn]

IMHO, just a Watts regulator is fine. Aren't all the Watts in-line rebuildable and all-brass (or bronze)? The semi-buried one I'm using (3/4") has been perfect in about 6-7 years of service, and it was used when I installed it.

 

[gwstang]

"...If you install a backflow protection valve on the house with the water heater on the downstream side you MUST, MUST, MUST install a thermal expansion tank for your water heater. If you don't and your heater fails in a way that causes it to superheat, the water can't back up into the supply lines and your water heater will turn into a rocket or explode, neither of which is fun...."

I have always thought that is what the blow off valve on the tank was supposed to prevent? I have heard of a tank blowing the back off of a house before though from someone who lived in that neighborhood. So, anything is possible.

 

[Valveman]

From what I understand, although some plans may deviate, but the water just flows from the tank by gravity to your house.

The city well pumps have a separate pipe running into the top of the inside of the tank and doesn't cause surges to a house. It is separate from the pipe going to the houses and it just tops off the tank to whatever the float level decides. If the pumps start it may cause a little turbulence when water splashes out of the pump tube, but not enough for any concern and wouldn't have any noticeable effect in a home. Just check some images googling, "How water tanks work."

When a well is right next to the tower sometimes they will just run a pipe to the top of the tower. But if the well is not close to the tower, most times they just tee into the distribution line and let the system pressure increase to fill the tower. This is when the system gets shock waves from the pump starting and stopping. Most water lines can handle fairly high pressure, it is the shock waves that causes lines to break. And since the main lines are breaking, I assume the supply pumps are teed into the mainline, which is causing the shock wave and line breaks.

 

[STx]

"...If you install a backflow protection valve on the house with the water heater on the downstream side you MUST, MUST, MUST install a thermal expansion tank for your water heater. If you don't and your heater fails in a way that causes it to superheat, the water can't back up into the supply lines and your water heater will turn into a rocket or explode, neither of which is fun...."

I have always thought that is what the blow off valve on the tank was supposed to prevent? I have heard of a tank blowing the back off of a house before though from someone who lived in that neighborhood. So, anything is possible.

TPVs fail and code requires the expansion tank on a closed loop system. When was the last time you tested your TPV? If you have somewhat hard water and you're not testing it yearly, odds are it will fail.

Here's a better explanation with code references. Looks like you should have one even if you only have the PRV, something I wasn't aware of since PRVs aren't common here. We're flat, so supply pressure is typically in the 50 - 60 PSI range.

Handling the pressure with expansion tanks << Home Improvement Stack Exchange Blog

 

[Deere Dude]

When a well is right next to the tower sometimes they will just run a pipe to the top of the tower. But if the well is not close to the tower, most times they just tee into the distribution line and let the system pressure increase to fill the tower. This is when the system gets shock waves from the pump starting and stopping. Most water lines can handle fairly high pressure, it is the shock waves that causes lines to break. And since the main lines are breaking, I assume the supply pumps are teed into the mainline, which is causing the shock wave and line breaks.

With a handle like Valveman, I bow to your expertise :thumbsup:

Everything in the house can break from pressure fatigue over time. If the mains are breaking from shock on startup, they need to have the pump start slower or get a smaller pump to get the pressure up first, or just fix the pipes.

 

[Valveman]

With a handle like Valveman, I bow to your expertise :thumbsup:

Everything in the house can break from pressure fatigue over time. If the mains are breaking from shock on startup, they need to have the pump start slower or get a smaller pump to get the pressure up first, or just fix the pipes.

It is not that easy. You can't "soft start or soft stop" a pump slow enough to prevent water hammer on pump start and stop. Even if the pressure is up, starting a pump of any size is trying to shove even more water into the system, and the pressure will spike.

Eliminating the pumps cycling on and off is the best way to get rid of water hammer. Starting and stopping pumps from a very low flow rate is then next best thing you can do. Starting a 50 GPM pump at 50 GPM or a 300 GPM pump at 300 GPM will cause water hammer. But if you start these pumps at 5 GPM, then open a valve to full flow, they will not cause water hammer. Same thing on pump shut down. Reduce the flow from 300 or 50 GPM to 5 GPM before shutting off the pump and there won't be any water hammer.

 

[Billrog]

I've been working when they need me for a utility company that services many water districts for a no. of years now.
We at times have to shut the water off for main line repairs but have never had a water pressure spike that would cause any damage when opening the valve back up it's done very slowly allowing the pressure to come up gradually & avoid air hammering. I'm sure anyone in the business would be aware of this.

 

[prichard]

I just want to point out that many utilities are going away from elevated tanks due to cost, maintenance and safety. I those cases the pressure is completely derived from pumps. This will still lead to fluctuations in pressure due to elevation.

In most elevated tank systems pressure switches pumps on or off, not tank level (even though theoretically the same). Pumps charge the system and also fill the tanks. I did controls for these systems for many years. If drastic surges existed we didn't do our job. Systems should never see surges that destroys equipment.