High Static Pressure Without a Fire Pump?

5/19/2026

Has anyone encountered unusually high and consistent static pressures in sprinkler systems where there is no visible fire pump?

I recently came across two examples that raised questions:
- A riser in our major metro showing about 165 psi static pressure.
- A five-story hotel with roughly 125 psi static pressure on every level, consistently throughout the building.

In both cases, I searched extensively for a fire pump and could not find one. The buildings were on normal city water supplies, not private systems or campuses, and there was nothing obviously unusual about the sites.

It made me wonder whether there are situations where some type of booster pump is being used for sprinkler systems without being readily identified as a traditional NFPA 20 fire pump? Or perhaps there is another explanation entirely.

Has anyone else seen this? If so:
- What was the situation?
- Was there hidden pressure-boosting equipment involved?
- Are there municipalities or systems where this is more common?
- Or is there another explanation for maintaining these pressures throughout a building without a fire pump?

Interested to hear what others have encountered.

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15 Comments

Pete H

5/19/2026 06:07:04 am

What did the flow tests at the nearest street hydrants say for the pressures?

anthony Crispo

5/19/2026 07:56:36 am

A five-story hotel with roughly 125 psi static pressure on every level, consistently throughout the building. -- For this one physics doesn't like it. You should loose ~ 20 psi from the first floor up to the 5th assuming 10 ft floors.

Most I've ever seen on a 'city line' is around 100 PSI static and that was on a dedicated Holly system.

I've seen several campus loops that are charged from a fire pump. So it would appear' as if the water is coming from the city but its a fire pump down by the main entrance. At a large stat university in the north east I has static at 140psi.

I've also seen at universities where buildings will use a shared pump. Building A has a pump then building B is built 25 years latter with the systems are tied together. Also have seen someone retire and no one knows how a building is run or pipe is routed.

Please do as-builts

Stevenn Gaillard

5/19/2026 08:12:03 am

This is really dependent on the location. I have seen flow tests in some areas where the static and residual were forcing PRV's without a pump involved. And sometimes the city has pressure pumps that are higher than usual. In particular you take Park City, UT they have high pressure pumps to push water up the mountain for snow making and such. They are continually at a much higher pressure than normal. Logan UT is also another area that its not uncommon for high pressures being supplied from the city.

Josh

5/19/2026 08:18:17 am

Have you checked to see if there's a campus pump that they may be on?

I had a similar situation with a hotel in Ft. Meyers, FL once where I learned entirely way too late that there was an entire development that had 2 private diesel engine pumps on it. They weren't even close to my building at all either.

Brett

5/19/2026 08:31:32 am

Did you try relieving the pressure by opening a drain valve or inspector test valve. Then check to see if the pressure returns to a high point? Perhaps a surge occurred or a pressure test was completed without relieving the excess pressure. If it returns to a high point, I would test the closest hydrant to see if it is at a similar pressure.

Dan Wilder

5/19/2026 08:44:19 am

Buildings at the low end of a water zone, especially fed from tanks or when the buildout of the upper part of that same zone occurred more recently all lead to high static situations. However, those have not gone above about 125PSI in my experience (unless a water hammer occurs).

Trapped air within large systems located in hot climates will often have excessive pressures if the system is not purged
Are you looking at the system side of the check valves for the gauge location? That leads me to believe that the check valves are holding well.

Is this building part of a larger complex? We have done seen shared supply buildings on the same property where the fire pump was located away from, or attached to a building, and completely separate from the other buildings on the property with no signage.

Have you put a gauge on a hydrant? Does the city of monitoring station data available to review? Can you put a recording pressure device on a hydrant in the area and let it record for 3-7 days to see patterns?

We had an ESFR TI that the flow test came back with the static pressure below the calc'd residual required even though the riser showed 20 PSI higher on the static in the system (the city water department does all the tests, so this was their people and their equipment from their department). Did the test 3 more times, all came back above but the FD required the lowest recorded. After putting a recording device on the hydrant for a week, we found out that a water bottling facility a mile away had expanded and refill their reserves 2x a day, but only every other day. One of our flow tests hit at that same time but when they stopped refilling, the entire system went into a small water surge and upped all the static pressures in the area.

Arthur Gould

5/19/2026 09:34:02 am

Far north Georgia 10" circulating city water main not far from Cartersville.

Test done by the county with a PE iwho knew what he was doing.

Static 127 psi
Residual 116 osu
Pitot 104 psi
Rate of Flow 1,711 gpm
Fire Flow @ 20 psi 5,845 gpm

The first ESFR system I have ever designed that did not need a fire pump.

5/19/2026 03:08:01 pm

That is a huge amount of water coming out of a single 2½" port....how much was it shaking??

Jack G

5/19/2026 04:34:46 pm

Physics, Boyles law, you have wet systems with small air pockets thru out. Initial ground water temp about 55 degrees.
A 1 to 3 % total air pockets with a 10 degree F rise in water temp compresses the pockets of air and could triple the water temperature. The smaller the air pocket the higher the pressure.
Reliable had a “ Texas trim kit “ that consisted of a half inch relief valve attached before the system side water gauge and piped to the exterior.
Now a days, air releases, are required on all wet systems to prevent this.
The name and purpose of the Texas trim kits was for big warehouse system s in Texas. High roof heat.
Had the same problem with a 100 foot high aircraft hanger. Between the lights heat and sun off the roof , the pressures would increase then go back to normal in the direction the sun took across the building,
( Air Force recorded pressures hourly before they agreed with me - reason was a change order was needed for pressure tanks on each system because they were foam water )
Air causing the problem. Any building, especially multi story.

5/19/2026 04:45:44 pm

Another consideration but not likely, reminds me of Salisbury Maryland and the Purdue corp chicken plant.
During the day, Purdue used so much water, the water mains in the street were about 35 psi. Water was being sucked out of water heaters and houses. About 6 am to 8 pm.
When they shut their use down each day pressure rose to 150 psi— plumbing had to be replaced , only rated about 90 psi)
We put relief valves on all the risers set at 165. Main BFP on loop supply.
Then we got a larger contract to put BFP s on all their customers water services . ( about 1968 )
Was an interesting puzzle at the time.

5/19/2026 04:50:08 pm

My apology—— air pockets affect water pressure ( not temperature in my initial explanation) thank you.

Ed K

5/20/2026 08:34:37 am

"It made me wonder whether there are situations where some type of booster pump is being used . . ." I've only seen it a couple times, but some older systems have an 'excess pressure pump' to keep pressure in the system higher than supply pressure. Other parts of the country may call these something different. They are a small pump about the size of a jockey pump and typically mounted on the system riser. They were sometimes used on systems with alarm valves to prevent false alarms. Flow switches with built-in retard function can serve the same purpose.

James Art

5/20/2026 03:05:33 pm

Yes, excess pressure pumps are a great way to solve a pressure surge problem.
Mostly for water flow switches. ADT used to have a great all in one product.
At the Oakland Air Port, they built what was then called the
World Airways huge aircraft maintenance hanger.

To serve the very large Foam Deluge systems
they built the whole building over a 1 million gal tank.
But even that was not enough water, so they had a 12 inch valve
open to refill the tank as the water was being pumped out.

The whole area was getting huge pressure surges, breaking
old WWII pipe in some former Navy hangers, and old underground, some corroded metal pipes due to salt water intrusion.

Turned out that their underground tank had slow leaks,
and when the float that refilled the tank closed,
it slammed shut, and created the high pressure water hammers.
Solution was a differed promise to fix the leaks,
and an addition 2" fill valve.

5/21/2026 08:01:10 am

Tx everyone, im cool insurance guy, so i cannot be flowing or tripping anything. There are many potential issues.

5/28/2026 03:52:58 pm

How cool? B. I was an insurance guy for many years, for both Kemper HPR, and for INA Combined Property. Yes, the insurance guy does NOT normally open the valves, etc. him or her self.
And yes, you want to be sure the water doesn't cause damage. But the idea is to WITNESS the testing, which can be done by the owner's rep or a contractor.

Incidentally, I designed an Embassy Suites hotel in Milpitas where the city pressure was 140 psi. I was able to get them to adjust the building total height to just under, instead of just over, 75 feet to floor of highest occupied level.
This made it technically no longer a "High Rise," so saved both a pump, and a tank. And many other features!

High Static Pressure Without a Fire Pump?

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