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Participant

Join Date: Aug 2010
Posts: 4

Black Iron Pipe for Fire Sprinkler System?

08/30/2010 11:44 AM

I have an old commercial fire sprinkler system (circa 1960) and need to move a sprinkler head. As far as I can tell the pipe is black iron and very heavy. There is an ASTM number on some of the pipe, but this number no longer shows up on any chart. Anyway, just to extend the pipe a few feet, could I just use black iron pipe from Home Depot, or is there anything special I should use. When I checked with a few fire protection supply houses, they sell schedule 40 black iron for sprinkler systems.

thanks

Marc

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Commentator

Join Date: Aug 2010
Location: Austin, TX
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#1

Re: black iron pipe for fire sprinkler system?

08/30/2010 12:29 PM

First of all, are you licenced to work on fire protection systems?

If you are not, I would highly reconsider what you are about to do. Of all the systems to have someone else maintain, this is one of them. Not only will you probably be violating a state and/or city code, your insurance company would crap a brick if they found out your were maintaining your FP system on your own - not to mention the building owner if you are a tenant.

The black iron pipe that they sell at Home Depot is Sch 40, but it is likely threaded to NPT tolerances AND NOT NPTF tolerances.

NPT and NPTF have different cuts. The NPTF forms a metal to metal seal when joined. You don't use teflon tape or pipe dope with NPTF - those would be used with NPT.

If you try to use the pipe from Home Depot, more than likely it would leak if you attached it to fire protection piping (again FP piping doesn't typically use teflon or pipe dope - which the use of would be a tell tale sign that a non licenced contractor had worked on a FP system).

Be careful.

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Participant

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#2
In reply to #1

Re: black iron pipe for fire sprinkler system?

08/30/2010 1:58 PM

OK thanks, I will look for black iron pipe threaded to NPTF tolerances. No I am not licensed to work on anything, that is a long and sordid story, but to make it short I just bought an old house and discovered that a previous owner had buried many of the ceiling sprinklers behind drywall. To fix this, the pipe sections need to be extended down about 4 inches each and new heads attached (the current ones are out of date).

I have called a bunch of licensed fire protection contractors and no one wants to touch it -- half the guys don't even return my phone calls. Best I can tell, it is because (a) the job is too small, and (b) it is quasi-commercial. quasi-residential and no one is sure what is required (it is currently residential but formerly a nursing home, thus the commercial system). One guy did look at the system and explained what needed to be done, but never came back to do the job. So, like it or not I think I am on my own. I will just do the best job I can and accept whatever consequences that entails.

Marc

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Guru

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#3
In reply to #2

Re: black iron pipe for fire sprinkler system?

08/30/2010 10:55 PM

Check the library for a copy of NFPA 13R (as in Residential) for some guidelines. You can DIY, and there is info in NFPA on what is or is not required.

I am not certain that NPTF threading is required, but dies should be available. Good luck with learning sprinkler pipe fightiing, ah fitting!

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#5
In reply to #3

Re: black iron pipe for fire sprinkler system?

08/30/2010 11:30 PM

Thank you for the information. I have been able to read the NFPA residential guidelines on their website, and they have been very informative. Of course my local fire dept can set their own requirements, so I have no guarantees of being compliant. (I am sure however I can do better than sprinkler heads buried behind drywall).

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#4
In reply to #2

Re: black iron pipe for fire sprinkler system?

08/30/2010 11:06 PM

Never-sieze will let the connections get tight enough to not leak.

buy a tap just to clean the threads

wirewheel the male threads

if possible air test to 10-20 pounds, using a dilute solution of soapy water, sprayed on the connections...

good job increasing the safety of your home

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#9
In reply to #2

Re: black iron pipe for fire sprinkler system?

08/31/2010 1:26 PM

Good morning Marc in MA,

If the previous owner buried some heads behind some drywall, the reason may have been a sprinkler system was not required in a residence of less than 3000 sf. If a sprinkler system is not required in your home, the fire department would not have any say in how it is constructed, right?

Are you just trying to make the system viable, since 95% of it is already there?

Could you remove a head and/or a down nipple to determine what threads you need?

I have not seen a residential sprinkler system, but the ones I have seen are exposed, a short distance down from the ceiling. I would imagine the best way to test the joints on an old system like that would be to remove the heads, cap the nipples, and hydrostaticly test the system. Could you do this with your system?

In aircraft hangers or barns, the sprinkler system is dry, kept pressurized by an air compressor, and is activated by a loss in air pressure. This is to avoid freezing. Is yours a dry system?

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#10
In reply to #9

Re: black iron pipe for fire sprinkler system?

08/31/2010 4:05 PM

As I understand it, the sprinkler system indeed was not required in a residence of this size. However, if further I understand the local fire inspector correctly, they also will not allow anyone to remove a fire sprinkler system once installed. Therefore, even though it would not have been required had it been used only residential for all these years, now it is there and must be maintained up to code. It is a kind of a catch-22. A further twist is that I am converting from 2-family to 3-family, and a 3-family in my town requires a commercial sprinkler system. Interestingly however, my occupancy permit for the 3-family does not include a fire dept sign-off to confirm that I actually have one. Either they are just not that organized, or it may be because the 3rd unit was already recognized as a legal non-conforming. Not sure exactly.

The system appears to be more-or-less functional, so yes I just want to maximize whatever fire-suppressing potential it may have. I think it is great to have.

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#6

Re: Black Iron Pipe for Fire Sprinkler System?

08/31/2010 12:03 AM

I worked in a pipe shop in the late 70's and everything was NPT, including sprinkler pipe and fittings. If you're just extending the pipes, use a steel coupling on each end and a schedule 40 pipe nipple of the right length.

As mentioned fire protection systems are usually dry, so doing an air test on piping buried in walls will be impossible. Leaks may be the reason the sprinkler system was abandoned. You may want to check local codes and building inspectors and your insurance company to see if you need the sprinkler system before reactivating it. You may wish to air test the system before you start working on it to find out the condition now and pipe openings you may not be aware of.

Also remember that a little pressure is all you need if you have a lot of pipe, you have a lot of storage volume to do damage if you have a leak or a rupture.

Pipe dope is commonly used to seal all pipe threads, no pipe dope guarantees leaks.

Years ago there was even special pipe dopes to seal poor threads, fittings that couldn't be replaced, etc.

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#8
In reply to #6

Re: Black Iron Pipe for Fire Sprinkler System?

08/31/2010 1:47 AM

Thanks, the system is currently active and pressurized. It has also been tested annually by the local fire department, but it appears to be just a cursory pressure test, they obviously haven't inspected much. The water flow detection system is intact and electrified, but the downstream alarm bell system has been disconnected.

Old Salt (thanks Old Salt) also mentions that NPT pipe with pipe dope may be an alternative. I am researching PST pipe sealant and several others mentioned here. At least if anything leaks, it will be easily accessible.

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#7

Re: Black Iron Pipe for Fire Sprinkler System?

08/31/2010 12:04 AM

I was the Maintenance Manager responsible for maintenance of sprinkler systems for many years. I was also Safety Manager for a lot of the time of my career. Wet sprinkler systems all use npt threaded sched 40 black pipe unless it is some exotic installation subject to corrosive vapors or such. Threads are usually prepped with either teflon paste dope or regular pipe dope because it is cheap and faster to apply.

If you are extending the drop pipes between the runs and the heads you have no problems as long as there are no unprotected voids between the runs and the heads.

If the system is circa 1960 and the heads have not been replaced since the system was built you will have to install new heads. By law, heads only have a lifetime of 50 years. They have a date either molded or stamped on the side of the base. That is the manufacture date. If 50 years or over replace them. If they are within a few years of 50 replace them too, get it all done at once since it is often a messy tack.

Good Luck, Old Salt

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#11
In reply to #7

Re: Black Iron Pipe for Fire Sprinkler System?

08/31/2010 4:15 PM

Well if normal NPT with teflon paste or PST will do the job that would make everything much easier.

I am also planning to change all the sprinkler heads to new (same specs), but was wondering if there would be any value to flushing each run of pipe in the process? I would imagine that there is some loose corrosion in the pipes, and I know this can sometimes cause problems by clogging sprinkler heads during an actual fire. I also understand however that draining and filling sprinkler pipes is when the most corrosion occurs. Would flushing the pipes be a good idea or should I leave well enough alone?

thanks

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#12
In reply to #11

Re: Black Iron Pipe for Fire Sprinkler System?

08/31/2010 5:10 PM

If the system is as old as 1960 certainly it would be judicious to flush it. This is usually accomplished by an "inspector's valve" located at the end of the furthest run. If you are not certain, flush as much as the system as you can gain access to. This is a very messy job. Use hoses with adapters at the removed head to direct the water to an area where it will do no damage. You will certainly be suprised at how dirty the system is. (this is also how dirty the extinguishing water would be if a head tripped or was activated).

The corrosion upon filling is caused by the dissolved oxygen in the water and entrapped air that uccurrs during filling. After you get the system flushed and filled up, leave it alone if at all possible, there will only be "one refill's worth of corrosion" that occurrs. The more you flush it and refill it in the future the more corrosion will occurr.

Good Luck, Old Salt

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Anonymous Poster (2); CoronaCameraMan (1); flyinghigh (1); Garthh (1); Marc in MA (3); MrGeneRall (1); old salt (2); Ried (1)

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