Keep Galvanized Pipe in Dry-to-Wet Conversion?

9/20/2022

I have a question about using galvanized pipe in wet-pipe systems. I have a building in which part of the building is wet-pipe, and part of it has a dry-pipe system using galvanized pipe in an unheated area.

Our renovation of the building is turning this space into a heated area.

My initial thought was just leave the existing pipe in place, convert the riser to wet-pipe, and make any minor modifications to the system coverage as needed.

As I've read more I'm not so sure. FM specifically says not to use pipe that has been internally galvanized on a wet-pipe system, and while it doesn't seem to be outright prohibited by other sources, I seem some strong recommendations against it.

If there is any experience out there on the subject I'd appreciate it.

At the moment I'm strongly considering replacing all system components and materials back to the base of the riser.

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11 Comments

Dan Wilder

9/20/2022 07:49:28 am

If you want a very angry client in as little as a couple months to a couple years, leave the galvanized.....eeck. While N2 inerting and addition of high point air vents will "slow" the process down, depending on the water supply, the pipe will develop leaks fairly quickly.

I would highly suggest replacement of any galvanized piping that is being converted to wet. Ultimately, it's up to the client but the investment now will be the better long term solution.

Is there an option to keep the dry system in the short term and approach the replacement in stages later on? I would also suggest a full inspection on the system (the 25-20 Ed. - 5 year per Chapter 14, but more locations) to establish somewhat of a baseline for the property. I'm not a big fan of the MIC testing as backup/proof because I have never received nor have heard of a test that didn't have MIC, it's always there.

https://nfsa.org/2018/12/07/an-introduction-to-corrosion-in-sprinkler-systems-its-identification-and-mitigation/

https://www.sprinklerage.com/galvanized-steel-sprinkler-piping/

I would also suggest reaching out to AGF, ECS, Potter, Southtek for options and solutions...no particular order.

Alex

9/20/2022 08:20:39 am

Replace the pipe all together.

The reason you dont use galvanized pipe in wet system is due to oxygen corrosion in water that will affect the pipe. Normally the Galvanized pipe is supplied with a nitrogen generator and pressurized to prevent oxygen corrosion.

If you put water in the galvanized pipe. you will have corrosion and leaks and subsequently complete failure.

Alex Riley

9/20/2022 08:54:51 am

Hi,

I would recommend replacing the pipe, as others above had mentioned. You will experience leaks before you know it if you leave it galvanized.

Alex

Glenn Berger

9/20/2022 09:08:23 am

I would love to say replace it all. How big of a project do you have? A full replacement will be no small task.

schulman

9/20/2022 09:15:32 am

galv pipe corrodes and leaks faster
here in my state the State Construction Office actually REFUSES Galv. Pipe on any jobs - dry or wet. Replace it if you have the money or wait for leaks.

Franck

9/20/2022 09:22:22 am

Just to confirm other comments : never use galvanized pipes for wet sprinkler systems and for areas where the ambient temperature could exceed 130°F.

When used for dry or preaction systems, it is preferrable to use an inert gas in the piping to limit the moisture content and oxygen level.

Julio Solar

7/20/2023 10:18:14 am

I understand, but we are by the sea (Florida) and our system is completely wet. We are having a lot of leaks due to corrosion in the black piping. As we repair them, we are doing it with galvanized. Again: our sistem is wet with pump and jockey pump with 150psi. Is it fine to use galvanized in a wet system? Thank you guys.

Pete H

9/20/2022 10:17:19 am

Replace the pipe if it's an FM job or if the pipe was originally submitted to FM specifications rather than UL listing. Replace the pipe if it's a "best practice" job. Replace the pipe if you have the money and the client wants to avoid leaks.

If the client's being so cheap that they can't handle the extra for replacing the pipe, look into UL and see if they're more lenient on galvanized pipe being reused in a wet system.

But you should replace the pipe. It's gonna leak.

DAVE

9/20/2022 11:34:58 am

I especially agree with Pete's answer here, as it is realistic by mentioning "best practice" and the client's money. I believe the owner should be made aware of the issues and risks so they can make an informed decision based on their situation, budget, and timeline. And document. But I think that's why the original question asked if there was any experience on the subject. As long as I have been in the business, I still rely on my most experianced field guys at times like this.

Jon

9/20/2022 06:05:30 pm

Well here in Saudi Arabia, galvanized pipe is common for wet sprinkler system. Pipe is hot dipped galvanized and we don't see any problem with leakage or corrosion. It is also sometimes being recommended in the project requirements

Chris

9/21/2022 07:57:00 am

If you're talking just a couple pieces I would switch it out without too much fuss. If you're talking about a pretty sizable amount then I would suggest having a conversation with the owner and putting the ball in their court. Personally I cant think of any projects where we had an issue with galvanized pipe on a wet system, the only issues we had were on dry systems.

Keep Galvanized Pipe in Dry-to-Wet Conversion?

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