Corrosion inhibitor on wet fire sprinkler water

[MedicineEng]

All:
Recently we started having a couple of events of pinholes leaks on our wet fire sprinkler pipe system.
Since these have affected some high end retail area in our property, obviously people are looking for some solutions/mitigation of future occurrences.
When we checked, the standing water on the pipe was heavy on rust, which is not exactly a surprise as this water might have been sitting on the pipe for a few years.
I thought about adding some corrosion inhibitor into the sprinkler water to try to extend pipe life.
We approached our subcontracted water treatment company, (one of the biggest in the world), that is managing our water chemical treatment on the boilers, cooling towers, etc. for a suggestion and the only thing that they came up with was to use a corrosion inhibitor that would require regular bleeding and water circulation.

In sprinkler system this is not feasible as there are hundreds of branches and not all have bleeding points. It would be madness to even try something like that.
We follow NFPA, so our system is pretty standard and I can't believe that we are the only ones with pinhole leaks in wet fire sprinkler piping network.
So I'm fairly puzzled by the lack of solutions from the water chemical treatment specialist.

Did anybody had same issues with sprinkler pipes?

Thank you all for your input

 

[LittleInch]

How old is the system and what is it made of?

Does it go off often / is it flushed regularly?

It's a bit odd as you would normally expect stagnant water to consume all the oxygen quite quickly and then do nothing, unless you've got some bugs in there.

CI works by gradually coating the pipe walls over time (weeks), but needs constant flow to do it.

Convert to a dry system?

Maybe it's just time to replace all the sprinkler pipes.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdStainless]

Most sprinkler systems are installed caring about the minimum code requirements and giving no thought to longevity.
I have seen systems installed to allow a continuous low flow circulation with inhibitors.
This works best when the system is very clean to start with and tightly sealed.
I have also seen sprinkler systems installed with sch5 316L SS pipe and swaged fittings (VicPress).
You also have to make sure that the inhibitor used is compatible with your sprinklers.
Your system needs to be drained and flushed.
Likely you have sprinklers that are plugged with rust.
And inhibitors only work if they can coat the surfaces.
Redesign to a dry system or replace and upgrade the existing system.

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P.E. Metallurgy, consulting work welcomed

 

[MedicineEng]

Thanks all for your feedback.
Replying some of your questions.

-System is around 7 years old
-It's made of galvanized steel
-It's not regularly flushed. Branches are only flushed when there are modifications to the network (addition/removal of sprinkler heads
-Replacing is not an option as the total length of the sprinkler system runs several kilometers

 

[LittleWheels]

MIC in a sprinkler system is a nightmare in my experience, if that is what you are dealing with. There were very limited options for remediation (other than replacement) the last time I had to look at the problem.

 

[LittleInch]

Oh dear.

Galvanised should last for a long time so I think you really need to see what type of corrosion you actually have and why it is leaking at those locations.

What type of water was used? - Potable "towns water"?
Was the leakage at pipe which was actually galvanised?
Was it at a joint? Was it screwed?

All rather odd as galvanised shouldn't be "heavy on rust".

SO you need to figure out if this is an isolated thing or if you need to start contemplating the worst case of replacement. Dripping rusty water on a tenants property doesn't sound like a good idea. But corrosion inhibitor sounds like it is a bit too late and far too difficult to actually administer.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[EdStainless]

1. Are you sure that it was all galv?
2. You will be replacing large sections of the system.
With deterioration of the galv and rusting it is likely that most of your sprinklers wouldn't work correctly anyways.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[LittleInch]

Did you cut out the leaking sections and examine them or were they just thrown away.

You might need to do some investigation and remove some sections and replace when you're able to turn off that branch of the sprinkler system.

Think you have some serious issues if galvanised pipe is leaking.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.