The Chicago City has a copious supply of natural water supply then why you should suffer from slow water rate. Plumbing is perhaps the most tedious aspect of MEP engineering. There is more to Chicago City residential plumbing than you would imagine. Not only does it require highly specific expertise, but should also be constructed an installed according to the rules and regulations outlined in the Chicago City Plumbing codes.

To understand how residential plumbing works, it is important to have some idea about pipes in general and cold water pipes in particular.

How Are Cold Water Pipes Different From Other Pipes?

There are two kinds of pipes that make up a conventional residential plumbing system:

  • Water supply pipes.
  • Wastewater drainage pipes.

The main difference between the two is, that water supply pipes are connected to the main water supply, and thus, are under pressure. Cold water pipes are also smaller than drainage pipes. These pipes further divide into hot water pipes, which are routed to the boiler or water heater, and cold water pipes, which supply water to fixtures directly.

Now, in most cases, domestic cold water pipes and hot water pipes are quite similar. The reason simply comes down to demand and preexisting pressure. Since cold water pipes are connected to the main supply, the cold water supply in fixtures is already available at the minimum required flow rate according to Chicago City’s Plumbing Code.


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How to Size Domestic Cold Water Pipes

Fortunately, the Municipal Code of Chicago has laid down very specific instruction regarding sizes of cold water pipes. These standards are derived by measuring the “fixture units” a value assigned to fixtures based on the amount of water they use. Since the size of a pipe has an impact on the flow rate, sizes have been set, based on which fixture the pipe is supposed to supply water to.

While you may have to do further research for determining the size of piping for a very specific or unusual fixture, regular fixtures most commonly use ½-inch piping. These include bathtubs, kitchen sinks, domestic dishwashers, most water closets, laundry compartments, and single head showers etc. Fixtures used from flushing mechanisms, such as the water closet flush valve and flushing rims on sinks need to be equipped with a ¾-inch or 1-inch pipe.

In case street pressure regularly fluctuates, piping sizes should be designed to account for the minimum possible street pressure. However, in cases where the street pressure is under the required pressure under section 18-29-604 of Chicago Plumbing Codes, you will have to install a water pressure booster or strainer, conforming to the section 18-29-606.5 of the plumbing code, since variation in sizes can only take you so far.

Maximum Flow rates for Plumbing Fixtures as mentioned in the plumbing code.

Plumbing fixture

Maximum flow rate

Sink faucet

2.5 gpm at 60psi

Urinal

1.0 gallons per flushing cycle

Shower Head

2.5 gpm at 80psi

Water Closet

1.6 gallons per flushing cycle

Lavatory, Public

0.5 gpm at 80psi

Lavatory, Private

2.5 gpm at 80psi

 Domestic cold piping networks are the lifeblood of all plumbing systems. So in order to have a better access to the flow of water the building water distribution system should be designed to have minimum pressure available.

You’ll find the indicative (not exhausted) list of minimum size as mentioned under section 18-29-604.5.1 of the plumbing code hereunder:

Plumbing Fixture

Minimum Pipe Size

Bathtubs

1/2

Bidet

3/4

Dishwashing machine

1/2

Kitchen sink

1/2

Laundry 1,2 or 3 compartments

1/2

Lavatory

3/4

Urinal Flush tank

1/2

Water Closet Flush tank

1/2

 Types of Cold Water Pipes

The Chicago Department of administrative hearings, rules and regulations have specified certain types of piping as fit for domestic use, based on the material they are made of. Without getting into the specific grades and varieties, the five materials you will commonly encounter on the market are copper, iron, brass, PVC, and galvanized steel.

For domestic cold water plumbing, here are the approved types of the pipe material.

  • Copper

Copper or copper alloys come in three varieties based on thickness; type M, type L, and type K, in order of increasing thickness. These types are approved under ASTM B 74, ASTM B 447 and ASTM B 251 standard.

  • CPVC

CPVC or Chlorinated Polyvinyl Chloride is a variant of PVC specifically used for hot and cold water pipes. Local codes require pressure ratings of PVC pipes to be stamped on one side. This type needs to comply with ASTM D 2846, ASTM F 441 and CSA B 137.6.

  • Galvanized Steel

Building trends have recently shifted away from using steel for domestic piping, however, it is not obsolete. Galvanized Steel is incredibly strong, making it suitable for areas where pipes are under load. You are required to use only those materials that comply with ASTM A 53 standard.

Materials like cross-linked Polypropylene or PEX is still a subject of debate in Chicago despite its competitive pricing in addition to all the aforementioned benefits of CPVC.

Regardless, it is best to call the local inspector before deciding what material to go for.

Protecting Your Cold Water Pipes

The Chicago plumbing code requires all pipes concealed in the concrete, cinder or any other material that has some lime and moisture content, to have a thickness of the at least 0.025 inches. This is because the lime and moisture react with the material of the pipes, causing them to corrode over time. Chicago engineers are also required to design adequate insulation for all pipes in attics, crawl spaces, or on the exteriors of the building, in order to protect them from freezing.

Your cold water pipes will also need to be protected from breakages. It is best to have the structural strength of the type of pipe being used in mind while designing the plumbing systems. Relieving arches may be required if the pipeline is going to be under too much stress. In cases where galvanized steel or cast iron is not used, it is best to use shield plates in accordance with codes to protect the pipes from any physical damage.

Most importantly, keep water pressure below 80 psi as prescribed by the municipal code. Otherwise, the pipes may start leaking.

Conclusion

A lot needs to be considered when installing a domestic plumbing system in your house, especially when it comes to cold water pipes. While the task of adhering to the extensive municipal regulations in this regard can be daunting, keep in mind that these codes are in place to ensure ease and safety for residents in the long run.

As far as design and practical applications are concerned, always remember to hire professionals who know how to take care of business. But that is no reason to not have all this knowledge at your disposal. Having an in-depth understanding of such systems will not only allow you to take better care of your home but also allow you to make more informed decisions.

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