Change Wet to Dry System Require Sloped Pipe?

8/11/2022

We have a wet pipe system in a conditioned space.

If this is converted to a dry pipe system for the purpose of installing a nitrogen generator - would the existing pipe need to be sloped?

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10 Comments

Ryan O'Hara

8/11/2022 08:05:15 am

Installing a N2 generator on an improperly sloped system will not have the same benefits of a system that drains correctly.

Why not just inert the wet system?

8/11/2022 08:09:35 am

My understanding of retrofitting systems with Nitrogen, is that a lot of the corrosion inhibiting is based on a properly installed dry system. A local nitrogen generator rep states that pipe having the correct slope is important for the nitrogen to do it's job properly. Plus, sloped mains and branch lines are requirements of dry systems in NFPA 13. I would say yes the pipe needs to be sloped, and maybe additional test and drains added as well. You should check out the nitrogen options for wet pipe systems. South Tek has an option available that I know of. It may be less hassle to leave the wet system in place and utilize a wet system nitrogen system.

Dan Wilder

8/11/2022 08:12:31 am

There is no distinction for Dry or Preaction piping systems for slope/pitch requirements for conditioned spaces, only for refrigerated spaces, the piping would need to be pitched per 13-19 16.10.3

Side question, why is it going to N2 AND dry? There are options for wet pipe inerting that my company has used successfully with nearly immediate positive results.

Rob B

8/11/2022 08:29:26 am

Unless I am reading this wrong, In general Dry piping needs to be pitched when installed?

David G Kendrick

8/11/2022 08:16:46 am

Agree with the sloping and additional drains.

Unless there is something else done to the system you'll need to survey the entire piping network and hydaulically calc the system for a dry system operating area for the protection required.

If that is possible then there is also the issue of pendant sprinklers in unconditioned space and not on return bends.

There should probably be, I said probably be an internal pipe inspection to determine the current condition.

Alex

8/11/2022 09:00:17 am

Hi,

The piping will need to be modified so it is pitched correct. Also, dry systems typically have a larger demand as well. Ensure your calcs work with the larger remote area.

Ensure to add additional drains, remove any low points/drops, ensure there are no drops to sprinklers.

Thanks,
Alex

Jesse

8/11/2022 09:25:02 am

Yep, you'll need to slope the branch lines and mains per NFPA 13. You'll probably need low point aux. drains as well.

Anthony

8/11/2022 09:52:28 am

Yes, all dry pipe need to be pitched per NFPA 13-19 and NFPA 13-16.

Kody Karch

8/12/2022 09:47:21 am

Unless there are other circumstances I am not aware of, wet pipe inerting would be your best course of action.

As efficient as N20 is, the water filled pipe will still have less oxygen in it than converting it to be filled with nitrogen only.

Chris Smith link

8/12/2022 03:52:48 pm

Needs to be sloped per 16.10.3.1 - Dry Pipe Systems in Nonrefrigerated Areas. In dry pipe system, branch lines shall be pitched at least 1∕2 in. per 10 ft (4 mm/m), and mains shall be pitched at least 1∕4 in. per 10 ft (2 mm/m) in nonrefrigerated areas.

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Change Wet to Dry System Require Sloped Pipe?

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