Residential Fire Sprinkler system (air okay?)

[SailorMan]

Hello All,
I have a question about a residential fire sprinkler system.

I live in a 25-year-old tract of homes with residential fire sprinkler systems. Ten days ago, the pressure sensor switch on my neighbor's fire sprinkler system failed. The rubber diaphragm in the unit leaked badly and by the time he discovered it there was significant damage to his carpet pad ...soaked carpet ...etc.

When these houses were built the city required the builder to have a pressure sensor on the fire sprinkler systems so that if the lawn irrigation system was on when a fire broke out in the house, the pressure sensor would sense the drop in water pressure in the Fire Sprinkler system and turn off the lawn irrigation system. This particular pressure sensor switch is listed for use on compressors, etc. but says nothing about being designed for fire sprinkler systems. I want to replace mine with another one designed for fire sprinkler systems.

It is a one-story house, the pressure sensor is down at the floor level and the sprinklers are (obviously) up in the ceiling.

MY QUESTION: When I disconnect the old pressure sensor switch, the fire sprinkler pipes will drain (at least partially) ...right? Then when I turn the water back on there will be air in the sprinkler pipes ...right? Do I need to bleed out that air somehow ...or is it okay for me to just turn-on the main valve and not worry about the presence of air in the (normally "wet") residential sprinkler pipes? Thanks in advance for the help.

-Patrick

 

[WorthFlorida]

I know very little about fire sprinkler systems and recommend a local company should do the work. It's possible that a residential property fire sprinkler system is a dry system and therefore an air pressure switch would be used.

As on commercial systems, the sprinkler system furthest sprinkler head from the water source is where it would be piped to a test valve for purging. By opening the valve is the same as a sprinkler head popping off and the system, tied to an alarm monitoring, would dial up a central station (alarm monitoring company) and trigger an audible alarm. It's a mandatory annual test for commercial buildings. The pipe should discharge somewhere outside. I do not know if a home system has this.

Have your neighbor call the insurance company. He may get some compensation for water damage and they should know who to call that does home fire sprinkler systems. I would assume the pressure sensor would be for a water pressure tank rather than an air pressure tank.

 

[Sponsor]

 

[wwhitney]

FWIW, I believe that these days that functionality would be handled by a domestic shut-off valve, like this:

https://www.tyco-fire.com/index.php?P=detailprod&S=9800

Not sure if it would be worth retrofitting one, they are quite expensive.

Cheers, Wayne

 

[SailorMan]

@Wayne: That valve is very interesting but no, it's not an option in this case. It certainly would be the way to go for new construction however. The simple way to solve my problem is by replacing the old low-pressure switch (which was never designed for residential fire sprinkler systems to begin with) with one that is designed for that purpose. I just need to know whether it's okay to install the replacement low pressure switch without flushing air out of the system. It is a "wet" system. I live in Western Washington State so the temperature can go below freezing for multiple days in the winter (the pipes are protected with insulation in the exposed attic because of this) but exceptionally hot summer days are very rare here. It's my understanding that air in sprinkler pipes (in an attic) can be a problem in areas that can have prolonged periods of hot days because the air can expand disproportionately and strain the pipes. These pipes are PVC, I believe. So I think it would be okay for me to have some air pockets in the pipes because they are insulated and they would never be subjected to intense heat in this climate.

@WorthFlorida: As mentioned in my original post, the pressure sensor switch is an electrical switch that switches-off the power to a single wall outlet in my garage - a dedicated wall outlet for the lawn irrigation system. So it is both a plumbing device and an electrical device. It senses a drop in the fire sprinkler pipe pressure and cuts off power to an electrical outlet.

 

[WorthFlorida]

Google "residential fire sprinkler system diagram" and you'll see that every diagram shows a test valve at the highest and further location. Somewhere in your basement there should be a drain valve, perhaps a pressure gauge and a control relay to trigger an audible alarm and signal a central station if so equipped. Once you replace the pressure switch, open the supply water valve, purge the system from the test valve and close the valve when the water flow steadily. The test discharge pipe should have a nozzle on it that emulates one sprinkler head water flow. When you run a test the water flow should trigger the system. If this is tied to a monitoring central station inform them that the maintenance is being performed so not to trigger an alarm to the fire company.
For six years (I worked at my church as maintenance director), I assisted the fire alarm maintenance company on this annual test and became fairly proficient on the Honeywell fire alarm monitoring equipment. A commercial fire alarm system has three different type of inspections and every three months something had to be tested.

 

[MACPLUMB]

What WorthFlorida posted
Licensed Fire Sprinkler Contractor

 

[SailorMan]

The PVC Fire Sprinkler pipes in the ceiling are all covered with a thick layer of loose fill insulation 12" to 18" high. I have dug through it in what looks to be the farthest point and I do not find a test valve. I'm beginning to think that perhaps it doesn't matter if air pockets are trapped in these pipes. The pipes are PVC so they are not going to corrode. Is there anything else that could be harmed by air in the pipes?

I don't have a basement. It's a one-story house. There is no audible alarm at all and no signal is sent to any central station.

Close to the floor level in a closet there is a drain valve, a pressure gauge and the above-mentioned pressure switch which allows 120volts to go to the lawn sprinkler outlet in the garage all the time unless it senses a pressure drop in the fire sprinkler pipe - in which case is shuts off power to the lawn sprinkler outlet.

 

[Jeff H Young]

Make sure whoever you take advice is qualified. Its interesting to me but I wont advise . I would like the answer too if air needs bled or not? A question to the OP after 25 years has a fire protection pro ever seen your system?

 

[WorthFlorida]

Without a test or bleed valve to purge air is probably why there is an air pressure switch instead of a water pressure switch. My first statement on the first post was get a local contractor in fire sprinkler systems.

 

[SailorMan]

@Jeff: Approximately ten or fifteen years after the homes were built there was a period of almost a week when the temperature went down to about seven degrees. The original system used copper pipes in the attic and they were not protected from the cold in the attic. The pipes froze, burst, and there was extensive water damage in several homes. Then there was a lawsuit. The sprinkler systems were retrofitted throughout the tract and this time thick insulation was placed over all the pipes in the ceilings of the homes. But of course the original pressure sensor switches were never touched and it's only now that the first one has started to fail. I, of course, don't want to become the second. Thanks Jeff for not advising.
EDIT (10/14/20): I have discovered that this account of a burst pipe in the fire sprinkler system (and subsequent retrofit) was actually a misunderstanding of statements made by a neighbor.

Everyone: Thanks to everyone who has posted in an effort to help in some way (it can be depressing when a thread gets zero replies). However, I'm only really looking for advice from persons who know the answer to this question about air in the pipes.

 

[Jeff H Young]

Good luck with it just didnt want to give bad info based on my guess. let us know what you learn. and glad your system has had some attention over years. BTW in my area CPVC pipe is often used in sprink lines similar to pvc yellowish glue orange pipe. Also curious if you were able to purchase your fire sprinkler parts as they keep a tight hand on selling to outsiders.

 

[SailorMan]

Yes, correct, it is CPVC actually. I haven't actually purchased the replacement sensor but it is available for sale openly.

 

[SailorMan]

Final Answer:
Based on statements made by a neighbor who's lived here much longer than I have, I was assuming that the fire sprinkler system in the attic was dedicated or separate from the normal residential plumbing pipes. I had nothing else to go by. But yesterday I finally connected with the right man in the city who knows the whole history of this RFSS and he explained it fully. I'm not sure what terminology the NFPA uses for this system (he referred to it as a "Flow Through" system) but it turns out that there is no separate or dedicated piping system for the RFSS. There is one system of (large CPVC) pipes in the attic. Both the residential plumbing fixtures and the RFSS Sprinklers are all connected to this single unified system - there is no isolation of the RFSS system at all.

So of course, my problem is now very simple. I simply shut off the main, switch off the circuit breaker and replace the pressure switch with one designed for this purpose.

The original pressure switch was a Mercoid CS-150. There is no mention of this pressure switch having been designed to measure water pressure - much less for use on an RFSS system. The plumber who removed the failed unit on my neighbor's house said it was "corrosion" ...and that would be logical - seeing as the unit was intended for use on "air compressors and other industrial systems". We should really be surprised if it were to have lasted as long as 24 years installed on a water pipe ...surprised that corrosion didn't catch up with it much sooner.

The documents given to the original buyers of these houses included no information on this RFSS and the pressure switch had no label telling what it was switching and the outlet far away in the garage had no label indicating that it was a switched outlet switched by a pressure switch in a closet in the other end of the house.

 

[wwhitney]

I think the current terminology for what you have is "multipurpose". There's a variant where only one or two toilets are connected to the fire sprinkler lines, those are called "passive purge". The configuration you originally thought you had is called "standalone".

https://www.finehomebuilding.com/2018/10/26/often-painful-evolution-residential-fire-sprinklers

Cheers, Wayne

 

[WorthFlorida]

Thanks for the update and information. There are plenty of articles and .pdf files out there.
http://www.phila.gov/water/wu/documents/rfss_qa.pdf

 

[SailorMan]

I think the current terminology for what you have is "multipurpose".
https://www.finehomebuilding.com/2018/10/26/often-painful-evolution-residential-fire-sprinklers
Cheers, Wayne

Thanks Wayne. That article was a very helpful starting point. The discussion about insulation helped me to understand the way the pipes in my house are insulated. There's a sheet of fiberglass bat insulation about 16" wide directly over the pipes and then there is loose fill insulation over that. The result is that the pipes have no insulation below but lots of insulation above so that some of the heat from the house below will reach them but the cold from the attic above will be reduced.

 

[Jeff H Young]

Good luck with project. The funny thing about that pressure switch is it could have been installed anywhere in the water main, but i guess since its there to compliment the fire sprinklers they install it in the sprinkler piping so that people dont tamper with it. I havent studyied fire sprinklers and never have worked on them and never would personaly unless I was working for a sprinkler contractor. Maybe you could have a sprinkler fitter check system when done