Wire Brush or Rust Inhibitor on Sprinkler Pipe?

5/26/2023

Our condo units are 23 years old. A recent inspection of the sprinklers had some rust on the exterior of the pipes near the sprinklers.

Can we wire brush these areas and spray with a rust inhibitor, or do we need to replace all those pipes?

Are other inspections needed to see if any rust is inside the pipes or how thick the pipe steel remains?

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7 Comments

Glenn Berger

5/26/2023 08:04:47 am

My recommendation is to have a licensed contractor perform some non-destructive testing to determine the pipe condition. Wire brushing or spray painting will just hide the problem.

Anthony

5/26/2023 08:11:28 am

Agreed on the solution, call 1 or 2 contractors to take a look and give you an opinion.

Only 2 things cause rusting pipe water from inside the pipe or water from outside the pipe. AKA a leak or environmental factors like other leaking pipes or the like.

If the rust is caked on and 'foamy' near a joint where the pipe turns, then it's probably a leak and that portion of the pipe will need to be replaced. If all of the pipe and fittings are brown and you have a humid climate it's probably just normal exterior oxidation.

Dan Wilder

5/26/2023 08:14:41 am

Exterior rust (not from a pipe leak, just atmospheric moisture) is common and really not an issue if it's light, especially without an active leak on steel pipe. Anyone recommending replacement at that minimal level to you, I would get a second opinion (again, assuming this is not an active leak and it's limited to surface rust).

Yes, you can take a light pressure wire wheel, Brillo pad, or other abrasive means to remove surface rust from the PIPES if it's an eyesore and then paint as wanted. There are products out there that you can just spray over the rust spots as well. Any pipe, fitting, valve, and/or hanger/pipe stand can be painted, but maybe take a couple pics of the pipe stenciling to allow a future company to see the type, schedule, & MFG of the pipe before it gets covered. Do not, under any circumstance, paint any sprinkler, pressure gauge, name plate, or external moving part (reset handles, springs, and the like...ask your current inspection company when onsite next)

As for wall thickness testing, there are several options from hiring a company to perform Ultrasonic testing of the piping system (up to specific lengths), spot checks of wall thickness, and up to having sections of the pipe cut out and sent in for testing at an approved lab. (We use ECS & Dyne but there are others that are just as good)

Your current inspection company should be doing internal inspections of the piping and valves every 5 years, flowing water yearly, and external system inspections per NFPA 25 (linked below for reference). Nothing more is required but there are preventative measures available depending on your budget.

https://www.nfpa.org/codes-and-standards/all-codes-and-standards/list-of-codes-and-standards/detail?code=25

Jesse

5/26/2023 08:44:57 am

I concur with Dan, this is likely just surface rust from ambient moisture. All of the solutions posted above are sound ideas

Casey Milhorn

5/26/2023 09:34:29 am

It sounds like you are an owner of the building or condo, or at least the rep for the owner. If so, ultimately it is up to you on repair vs replacement. Two things: 1. Reliability and ability of the system to perform and 2. possible future water damage cost.

Not having any pictures, but going by the description, I would rate exterior corrosion at about a 2 out of 10 of affecting the system performance/dependability. Probably a 4 out of 10 on possible water damage concerns (depending on location of pipe: garage, in the unit, etc). If exterior corrosion is prevalent for your location, I would be even more concerned on the sprinkler heads themselves. As they say, an ounce of prevention is worth a pound of cure. Or in other words, a little $ now, or the possibility of a lot of $$$ later.

Franck

5/26/2023 03:34:14 pm

I agree with Dan and Jesse
If this is a wet system, outside corrosion might only be related to ambient humidity level (or maybe salty environment if you are near the Sea), and most of the time not a real concern for corrosion inside the pipes. Just clean it and it should be fine for another 10 years or even more.
If you have corrosion inside the pipes, this is another issue as it could expand being unnoticed until you have a failure. Or create “sediments” that may block your sprinkler orifices (especially if installed pendent).
If you have corroded sprinklers, then replace them (especially those with a fusible link).
If you have dry sprinkler system, then it is wise to inspect the inside of the piping.

Frank Savino link

6/2/2023 09:26:54 pm

The rust on the outside of a pipe is oxidized steel that provides a non reactive coating that actually inhibits further oxidation. Removing the rust will expose metal that has not been oxidized and which is susceptible to oxidation and further deterioration. Therefore, do not remove the rust. It is actually providing protection of the pipe.

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Wire Brush or Rust Inhibitor on Sprinkler Pipe?

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