Nitrogen for Small Residential Dry Pipe Systems?

11/22/2023

Is it worth installing a nitrogen generator for small residential dry pipe systems with less than 50 gallons?

We have about 175 homes with dry pipe systems in our jurisdiction.

Would a nitrogen generator be the best solution for corrosion protection?

Thanks in advance.

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19 Comments

Daniel

11/22/2023 07:47:08 am

Is the area conducive to the production of iron oxide? If CPVC is used rather than steel, I would consider air acceptable.

James

11/22/2023 07:49:04 am

CPVC can't be used with dry pipe systems.

Nitrogen is excellent at eliminating corrosion, however the cost/benefit for smaller systems would get tricky. I would be really interested in a lifecycle cost analysis like they often do for energy codes on the mechanical side. There'd have to be payback, just depends on how long it'd take to break even.

Daniel

11/22/2023 07:54:29 am

Thanks for the info James, that makes sense. Still learning over here.

James

11/22/2023 11:02:02 am

Daniel - I spoke too soon - learned something myself today.

Blazemaster is listed for low pressure residential dry sprinkler systems (limited to light hazard and residential occupancies, pressure not over 15 psi, ambient temp above -20 F).

I stand corrected. Glad you mentioned it. Kudos to Dan and Bill (below).

Jesse

11/22/2023 09:13:00 am

It won't be CPVC if its a dry system.

11/22/2023 08:18:40 am

1. If corrosion is a concern, I would use schedule 40 pipe and make sure the pipes are pitched correctly when installed before suggesting anything else because no one maintains residential fire sprinkler systems. The more system components are installed the more system components need to be maintained in the future.
2. Vapor pipe shield is less expensive than nitrogen if the houses are high end and want to pay for an extra level of corrosion protection (see the link below).

https://www.generalairproducts.com/fire-protection-products/vapor-pipe-shield/

Mike M

11/22/2023 08:20:45 am

I'm not aware of any "small" systems, most of the commercially available stuff is definitely not going to be cost effective at that system size that I have seen. That said if your drainage is good you could consider a drier (dessicant or refrigeration), and/or if the system is tight and that small you could use bottled nitrogen to charge it and even as a permanent supply as long as someone is going to be dilligent to change the bottle out once in a blue moon. Schedule 40 and cut groove where it makes sense might be worth considering as well.

11/22/2023 08:21:03 am

I would go with all sch. 40 piping (black would be fine, galvanized pipe wouldn't see enough advantages for a residential install) before installing a nitrogen generator for such a small system. Nitrogen generators would be costly for such a small install, and on the technical side they are not as easy to maintain as an air compressor. Depending on the air compressor used, a dryer might be an option too, which will lower the moisture content in the air supply. With current NFPA 13 codes, a permanent nitrogen generator can yield a 120 c factor to aid in hydraulic calculations, but with such a small system I don't think this would be a big selling feature here.

You could also supply nitrogen tanks for the system, however it is not a permanent solution and will require a reliable source for a nitrogen delivery. It would probably be the most efficient way to supply nitrogen, but I am unsure of how often a standard 2700 psi tank would last for a 50 usgal system. I would imagine years, but may be someone can speak to this.

Glenn Berger

11/22/2023 08:43:09 am

I have been on the N2 train for over a decade now. I would recommend nitrogen be used regardless of the size of the system.

J esse

11/22/2023 09:17:39 am

I'm not sure the expense would stand up to a cost benefit analysis

Dan Wilder

11/22/2023 09:38:37 am

In lieu of N2, available by ECS, General Air, & Southtek (& a couple others)....

Use CPVC and a low-pressure dry system (<15PSI) valve if you can comply with the minimum temp being above -20 and water to the remote sprinkler within 15 sec. Both Spears and Blazemaster allow dry pipe installation (link & page at bottom).

There may also be an option for Antifreeze if the system is small enough and compatible with the CPVC (<500 gallons for 13D & 13R)

General Air has the new Vapor Pipe Sheild as well.

https://www.generalairproducts.com/fire-protection-products/vapor-pipe-shield/

https://iq.ulprospector.com/en/_?qm=10005:7925~10008-!:6&se=LS&p=10005,10008 (may need to log in)

https://spearsmfg.com/flameguard/03-FG-3_0321_web.pdf - Page 8

https://www.vikinggroupinc.com/sites/default/files/documents/080712.pdf - Page 33

Bill

11/22/2023 09:53:51 am

Blazemaster CPVC is listed for low pressure dry systems

James

11/22/2023 10:59:38 am

I learned something new today. Wow, this seems like a really big deal for 13D residential. I've put some thought into it for my next home and have been interested in figuring out a way to do cost-effective dry systems (potentially for attic protection, though I haven't looked through all the literature yet)..

Found this just to confirm myself (page 33): https://www.vikinggroupinc.com/sites/default/files/documents/080712.pdf

Dave

11/22/2023 01:52:39 pm

I don't do mush residential anymore, but thanks, was not aware of that option either.

Casey Milhorn

11/22/2023 11:21:32 am

Dan nailed it as usual. Sounds like you have existing 13D steel pipe dry systems. So CPVC is already out of the question.

I would look into the vapor shield. Great product and especially economical in the smaller sizes. You might reach out to Ray directly at General Air to see if he has any "micro" systems in the works. if not, and you had a market for these, might be a great opportunity for some test projects.

The other alternative is converting to anti-freeze systems. I bet these were installed during the antifreeze "ban" and that's how they ended up dry. Should be acceptable now, but you still need to watch out for trapped air pockets, especially since the systems are sloped. Might need air vents. If it makes sense, go this route. A lot better than having to deal with a dry system in a house from a maintenance perspective. Just gotta make sure the anti-freeze is tested on a regular basis.

Patrick Drumm

11/24/2023 09:13:05 am

I've heard only good things about the vapor shield product up here in the Northeast. I have not personally designed or witnessed the installation of one of the systems, but my industry contacts that I have asked have praised the product. I've checked out their webinars and the science behind it is really interesting to me. The idea of a "micro" style system of this kind is very intriguing. So many projects have overhangs, exterior decks, etc. that require a small dry system. A lot of options are cost prohibitive, but if a less expensive option were developed, I think it would be widely accepted.

David Kendrick

11/22/2023 12:25:55 pm

Reliable makes a Nitrogen manifold for compressed gas in bottles. No generator involved.

https://www.reliablesprinkler.com/product/nitrogen-automatic-pressure-maintenance-devices/

Certainly another choice.

Frank Savino link

11/24/2023 08:47:21 am

There are compact low cost nitrogen generators that are feasible for this application.
Be careful with chemical corrosion inhibitors. The purge vent cannot be discharged into an occupied area.
If you want to avoid these added system costs, use schedule 40 black pipe and be sure to pitch to drain properly. Get all standing water out. Do not use schedule 10 and galvanized pipe.

Sean

12/31/2023 11:15:10 pm

short answer no

Nitrogen for Small Residential Dry Pipe Systems?

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