From the 17thth century, cast iron pipes played an essential role in the transport of water, gas and sewage. And while modern pipes like PVC and CPVC are becoming more popular, there’s still something undeniably classic about cast iron.
Cast iron pipes are often the standard plumbing system in many old and renovated homes. And while they may look dated, they are versatile pipes that can still connect with modern designs almost perfectly.
So whether you want to fix a broken pipe, connect your system to something new, or do standard maintenance, connecting a cast iron pipe is surprisingly easy.
This article explains everything you need to know about connecting cast iron pipe to your system. With our help, we will help you secure everything in your home.
Equipment required
Different connection techniques require different equipment. An extensive list of all tools is below:
- Cast iron pipes
- saw (if cutting)
- Pipe lubricant
- Pipe couplings
- Compression seals
- Pipe lubricants or adhesives
- Socket wrench, screwdriver, screws and bolts
- Oak and iron
- Molten lead
Step by step guide on how to connect a cast iron pipe
Despite being ancient, cast iron pipes are surprisingly versatile in relation to other types of pipes – as long as you have the right equipment, accessories and technique.
How you connect them can depend on where they are located (underground or not), whether they are placed vertically or horizontally, and what type of pipe they connect to.
Today we’ll explore the most popular ways to connect them below – hubless joints, couplings and compression fittings, and discuss the different types of pipe and the considerations you need to keep in mind when connecting them horizontally and vertically.
Method of hubless couplings
- Before you begin, make sure each pipe end is smooth and clean. The edges of the pipe must be a clean horizontal cut; avoid pipes with diagonal ends. Also, make sure the gaskets and coupling you are using are clean and undamaged.
- First place a coupling on the pipe. Please do not push it too far as you will pull it back over the gasket.
- Place the gasket on the end of the pipe until it hits the cast shoulder or it won’t go any further. Then connect the second pipe to the gasket as far as possible.
- Now slide the coupling over the gasket. At this point, both pipes should look connected.
- Using a torque wrench, tighten the stainless steel clips of the coupler from the inside to the outside, alternating between the two. You should hear a «thud» when the pipes are properly connected.
- Depending on the coupling, you may need a 60-inch, 80-inch, or 120-inch torque wrench.
Compression seals
- Make sure the pipe hub, joints and pipe ends are clean and all sharp edges have been removed. Again, make sure the pipes used have a clean horizontal cut.
- Fold the gasket and insert it inside the pipe. Use a rubber mallet to make sure it is fully seated.
- Coat this end with pipe lube, making sure to protect your eyes. Larger cast iron pipes may require an adhesive.
- Align the second pipe and insert it into the spicket. The gasket should expand and form an incredibly tight seal around the second pipe.
- If you used glue, make sure the pipes connect properly before it has a chance to harden. Moving the pipe can damage the structural connection.
Pro tip: If you are using the compression gasket method in a cold environment, you should soak the gasket in warm water so that it remains easy to work with.
Connecting a hub and a cast iron soil pipe (caulk)
A caulked joint is used in cast iron pipes when there is a hub end and red. These connections were common until the 1950s and are a common sight for people repairing and replacing older systems.
- Clean and dry the pipe ends and be sure to wear protective equipment (including goggles).
- Align the end of the tube inside the hub of the other tube.
- Put oakum (fiber) into the joint using the iron to create the seal.
- Next, pour molten lead into the joint, filling the top of the hub. The lead will solidify in about 2 to 3 minutes.
- Once cooled, you can caulk the pipe inside and out with a caulking iron.
Tips for horizontal and vertical connection
Connecting horizontal pipes
For horizontal pipes, be sure to use a leveler and get a gradual slope from one end of the pipe to the other. YouTuber How2Plumb recommends using a minimum of a quarter inch per meter of pipe to slope your plumbing system.
This amount ensures that the pipes will work properly and prevents the contents from flowing back. For hanging pipes, ensure that each length of pipe is supported by a hanger no more than 18″ apart from the horizontal connecting joints. You can tilt hangers to help add or correct slopes accordingly.
Connecting vertical pipes
One of the most important factors to consider when connecting standpipes is that they are properly supported throughout the plumbing network. After all, cast iron pipes are heavy and should be able to withstand their own weight, the weight of the pipes above them, and the weight of the contents they carry.
Use stakes or braces to properly secure them on each floor and at the base of the sanitary system. Place supports under the hub or elbow of the pipe to prevent it from slipping over time. You can also use a lifting clamp to help «ride» the pipe into a permanent, upright position.
Extended tips
- Although you can cut cast iron pipe by hand or with power tools, always make sure you get a square cut, that is, straight down. Avoid diagonals or angles.
- Test a pipe for cracks, breaks or damage by running water through it before connecting it. A plumber’s epoxy can be used to repair minor defects.
- If you are replacing cast iron pipes, consider lining the new pipes with acid resistance. This will not only protect the pipe from corrosive damage, but should extend its life considerably.
- Regardless of your method, the basic installation procedures remain consistent – ensure a tight seal between pipes at all times.
- Despite their age, cast iron pipes can connect perfectly with PVC and CPVC pipes, as long as you install the appropriate connectors.
- If connecting cut cast iron pipes, remove sharp edges. Sharp edges can make it very difficult to join the pipe with the gaskets.
- The joints can only work with a maximum deflection of 5 degrees, at which point they will fail. If you need more bend, consider using a fitting.
- When cutting pipes, be sure to wear protective equipment and properly secure the pipe. Use a quick cutter or diamond blade and follow the relevant safety procedures.
- Horizontal cast iron pipes must be supported at each hub or coupling. Make a quarter-inch slope per foot along the pipe.
- With vertical pipes, support them at the base of the system and at regular intervals (like any floor). This helps alleviate the weight of the top pipes and their contents. Use straps, braces or clips to reinforce their position.
- If you connect pipes at low temperatures, warm gaskets and joints beforehand by immersing them in water. This loosens the fittings, allowing them to join more easily.
- Avoid inserting cast iron pipes bogs, peat bogs or salt-laden soils, because they can rust the connections faster.
- Cast iron drain pipes can suffer from rust, corrosion and abrasion from dirt, gravel, sand and other debris inside. Use cables or hydro-jet to maintain them and make them last longer. You can also use a water softener to control the pH found in your pipes.
Conclusion
Cast iron pipes are a classic way of carrying water, sewage and gas around our homes, towns and cities. They can even be used for venting or transporting gas, and despite their likelihood of rusting, these soundproof downspouts are still an extremely popular form of plumbing.
In addition, old cast iron pipes can be connected to modern PVC pipes with just a little patience, guidance and the right equipment, making them a versatile option.
With our step-by-step instructions, homeowners of all skill levels can connect pipes safely and securely, ensuring they stay in place and functional for years to come.
That being said, if you have any questions about the process, leave a comment below. But when in doubt, remember these three crucial points when evaluating the task ahead:
- Cast iron pipes require tight joints and gaskets to connect properly. Warming these parts before application can help to secure them.
- When laying horizontal pipes, make sure there is a gradual slope to the system.
- When running vertical pipes, ensure adequate support for the weight of the pipes.
