Fire Sprinkler Systems

[JEuriech]

Fire Sprinkler Systems

I am starting to see more fire sprinkler systems in new homes. I currently do nothing with sprinkler systems and I disclaim them in my report. However, I do open up the fire sprinkler panel and check for missing insulation, if the panel is on the inside of an exterior wall. (also look for any obvious water leaks)

Recently, I have found the water pressure gauge inside the panel to read around 100 psi while the incoming water pressure to the house was only at 75 psi.

I curious as to why the sprinkler system is at a higher pressure? There are no pumps on the system and it is only fed by city water. Are these systems tested at a higher pressure when they are installed? Are pressures the same on a wet pipe and dry pipe systems?

Thanks

Jeff Euriech

Peoria Arizona

[ozofprev]

Hi Jeff,

My home has a sprinkler system. The gauge on mine shows 90psi. It cannot be higher than the pressure to the house.

Possible causes for what you are seeing:

1. The gauge for the sprinkler system is not calibrated correctly or is broken.

2. The reading you took is not the actual pressure to the house. The location at which you took the reading is important.

3. Your gauge could be broken or incorrectly calibrated.

I check my system annually. I paid once for a 'professional' inspection and won't waste my money on that again. I would not check a system other than mine, but the check is essentially:

1. turn the bypass valve to drain some water. This sets off the alarms (indoor and outdoor).

2. listen for the alarm and look at the gauge. The gauge will drop.

3. return bypass valve to its original position.

4. check that the gauge returns close to what it was prior to turning the bypass valve. Of course the alarms should be silent now.

If the alarm is connected to ADT, Brinks, or whatever, you need to give them a call ahead of time. Mine is not.

You are likely seeing more sprinkler systems because fire departments are recommending them in homes located in cul-de-sacs - as mine is.

[Jesse]

Originally posted by JEuriech

I curious as to why the sprinkler system is at a higher pressure? There are no pumps on the system and it is only fed by city water. Are these systems tested at a higher pressure when they are installed? Are pressures the same on a wet pipe and dry pipe systems?

Dry pipe systems are usually located in areas subject to freezing, such as a portico, loading dock, etc. They are maintained, by a pump, at a lower pressure than the incoming water supply. (It's isolated from the supply pressure.) When a sprinkler head is activated by heat, the pressure drops even lower, allowing water into the system and to the activated head.

Systems are tested at a higher pressure when installed. I am suprised, though, that you found pressure in the system that exceeds that on the supply. Sounds like a bad gauge, or at least a faulty reading.

I haven't heard of departments defining residential sprinkler requirements according to proximity to a cul-de-sac, but I know that Fire Prevention Bureaus are pushing for them in residential construction more and more. They are relatively inexpensive to install during construction. If you have one, learn how to shut if off. The fire goes out, or is kept under control, but the amount of water put out by just one head creates a lot of damage.

[kurt]

The day all new homes have suppression systems will be a good day. Massive infrastructure, expensive fire department maintenance, and less than satisfactory response times all point to private fire suppression as a good idea.

Build smaller, safer houses.

The only thing I find silly is when the single new home on a block of 100 year old homes is required to have suppression. Where's the benefit? (the pipefitters union....)

[Brian G]

Originally posted by JEuriech

Recently, I have found the water pressure gauge inside the panel to read around 100 psi while the incoming water pressure to the house was only at 75 psi.

How much time passed between the two readings? If it's a closed system, and many are these days, the water heater kicking on could have raised the pressure during the interval. Just a thought.

Water is weird. You can't compress it, but if you heat the stuff it expands.

Brian G.

Water + Heat = Expansion = Pressure [:-bulb]

[Scottpat]

Could it be that the house plumbing had a PRV on it and the fire suppression system did not?

I found a house a few months back that the incoming line from the meter split and supplied water to the house and the law irrigation system. They placed a PRV on the house side of the supply line at the water heater and not on the irrigation side. The owner could not figure out why sprinkler heads and lines kept blowing out! When I tested the pressure on the irrigation side it was right at 120psi.

[Brian G]

Originally posted by Scottpat

I found a house a few months back that the incoming line from the meter split and supplied water to the house and the law irrigation system.

Well lord knows the law needs irrigating. []

Brian G.

Or Is It Lawyers We Should Irrigate [:-crazy][:-sour]

[Jesse]

Interesting point, Scott. High water pressure is generally not a problem around here, so that didn't even cross my mind. Thanks.