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The necessity of grounding your plumbing can be confusing if you are not an electrician or plumber by trade. Does your plumbing need to be grounded and if so, why?
Your piping–if it is primarily composed of metal–should be bonded to your electrical system and its grounding electrode. Your plumbing needs to be grounded to prevent damage to your electrical systems, yourself, or any other residents in your home.
Grounding standards are complicated and heavily dependent on local building codes. Let’s go over all of the reasons your plumbing should be grounded, what can affect that, as well as some specifics behind the practice.
The threat potential of ungrounded plumbing
One of the more common materials used for pipes is copper. While this material comes with plenty of benefits, it also comes with a few potential risks.
Metal water pipes are excellent conductors of electricity. Metal water pipes can conduct electricity into a building and damage your electronics if they happen to cross your plumbing.
This current has a few potential sources:
- A nearby building with an open neutral
- Lightning strikes
- Faulty wiring or electronics
Wherever the unwanted current comes from, ungrounded plumbing poses a potential risk. By grounding your metal pipes you can add an extra layer of electrical protection and avoid accidents.
Grounding your plumbing will also provide a grounding electrode for internal faults in your electrical system. Your plumbing can become a safe direction for the electrical current to find the ground.
That said, grounding your plumbing is not the only way to protect your electrical system. Be sure to consult an electrician if your home needs further grounding.
Oftentimes having your plumbing system as a grounding electrode is not enough to prevent bodily harm.
Pipe material affects grounding needs
Water pipes and plumbing, in general, do not always make use of metal. There are five main materials used for plumbing.
These materials will determine whether your underground pipes can be used for grounding or not. The two main types that these five fall into are metallic and non-metallic.
The two metallic materials are copper and galvanized steel or cast iron. The other three are polyvinyl chloride pipes (PVC), cross-linked polyethylene (PEX), and acrylonitrile butadiene styrene (ABS).
While each of these materials has its own characteristics, what matters at the moment is its conductivity. Compared to the metals, the last three are not conductive.
Since PVC, PEX, and ABS are not especially conductive, they would not work as grounding electrode conductors (GEC). The metals, copper in particular, are electrically conductive.
Since this is the case, according to section 250.50 of the National Electric Code (NEC) underground water pipes made of metal must be bonded to the grounding electrode system.
Another condition is that the pipes must have 10 feet of direct contact with the earth. However, it is primarily the metal that determines the necessity for grounding.
This does mean that anywhere the metal pipe is replaced with a non-metallic material it must be bridged.
Bonding or grounding?
You will likely hear both grounding and bonding thrown about in relation to your plumbing system. While both are important when following building codes, you may not need to worry about bonding as much as grounding in this context.
That said, in some cases, you may need to bond your plumbing before or even in order to ground it. As mentioned at the end of the previous section, if portions of your primarily metal piping are PVC or another non-metallic material you will need to bridge the gaps.
Bonding the pipes across gaps is modeled in this video. This is one way that bonding is used.
Bonding is simply connecting two or more conductive materials by a conductive path. Additionally, metal water pipes are not relied on to be the only grounding electrode.
This means that bonding is used to connect them to the electrical system and the secondary electrode.
All of the conductors that don’t normally carry current should be connected or bonded to form a low-impedance path for any ground fault currents.
However, if these conductors are not then connected to a grounding electrode conductor it does little good. So both bonding and grounding are important when considering your plumbing system.
How is plumbing normally grounded?
As you can imagine there are many ways to accomplish the goal of electrical system safety. If your plumbing system is primarily non-conductive, obviously that system won’t be grounded.
This is only necessary for metallic plumbing systems. When the pipes are mostly metal there are a few ways to go about grounding the system.
It depends on whether the underground pipes are metal or not. If it is only the internal pipes that are made out of metal the electrician grounding the system will have to install a grounding electrode.
In the case where the underground pipes extend at least 10 feet into the earth, they will form the grounding electrode. All that remains to do in this case is ensure the pipes make a continuous path and bond them to the electrical system.
According to section 250.104 of the NEC, the plumbing system must be bonded to the electrical system enclosure or a couple of other options.
If there is not at least 10 feet of metal piping in the ground the grounding electrode must be added. This consists of a highly conductive metal rod inserted into the ground.
The internal metal pipes and electrical system are then bonded to this metal rod. As with the previous case, the metal piping must be made continuous if it is not already.
How to check if your plumbing is grounded
If you have metal water pipes but aren’t sure if they are grounded already or not you will want a way to check. The most reliable way to check is to bring in an electrician.
They will know where to check and have the tools already. However, you can do this yourself if you have the tools and the desire to.
Remember to always practice caution when doing DIY electrician work.
What you’ll need is a multimeter to check for voltage and access to both your electrical panel and water pipes.
First, try a visual inspection. Look at the cold water pipe for any wires connecting it to your electrical panel. These wires will be connected by clamps. If they are simply wrapped around you may have a non-professional job attempt on your hands.
If you do find a clamped wire check to see where it goes. If it looks intact and connected to your electric panel you have a grounded pipe system.
If your visual inspection turns up nothing the grounding connection may be hidden or isn’t present.
This is where the multimeter comes in. Connect your multimeter to your pipes and check for voltage and ohms. You should pick up 0 (or very low) volts. The ohms should also be low.
Now that you know why plumbing needs to be grounded you can check your own home. Keep in mind that your water pipes should not be the only grounding electrode.
Additionally, local codes may or may not adopt the NEC. Check local codes to ensure you are following them.