FOR PROPERTY OWNERS
If you are a do-it-yourselfer on a home project and you run into a situation where you find yourself dealing with an electrical conduit that contains concrete, this is when it is probably time to call in the professionals. The tools, chemicals, and procedures involved require trade expertise and specialized safety equipment; therefore, contacting a licensed electrical contractor will probably be your best bet.
FOR CONTRACTORS
Dealing with a conduit filled with cement can be a very challenging field problem to face, but it may be possible—with the right approach, right tools, and professional-grade concrete dissolvers—to remove the cement without replacing the conduit.
When concrete or mortar finds its way into electrical conduit and hardens before the wire has been pulled, this presents a unique set of problems. Pulling the wire at this point may be impossible, or if it is possible, the wire may be damaged and won't be fit for service. At this point, you will need to either remove and replace the section of conduit. If you are lucky and the conduit is accessible, then replacing it is probably the best way to proceed. However, if replacing it is the last option due to the expense and time required to gain access, it might be time to consider other possible options.
The other options involve removing the concrete deposit from the inside of the conduit. Hydro jetting is one option. This can usually be done with a high-pressure hydro jetter if the deposit is minimal or not fully hardened. If the conduit is made of PVC, then chemical dissolving is another option. A concrete dissolving chemical that actually works, such as Croc-Crete, which is specifically engineered to dissolve concrete and its variants, can be used to dissolve the deposit without harm to the PVC conduit.
It is a multi-step process to follow, but when properly implemented for a successful outcome, it can save huge amounts of time and money if the only other option is digging up a road or destroying a foundation to replace the affected conduit. A conduit blocked with concrete can really cause a serious setback on job progress if the conduit can't be easily replaced or the concrete removed.
Chances are, if concrete has found its way into the conduit, then more than likely the conduit itself is going to be located and running through a poured concrete slab or raceway. The main problem with conduit being filled with concrete is that, unfortunately, it's usually hard by the time it is discovered. If it's discovered while it's soft, then it's just a matter of getting the jetting equipment out there on site immediately and jetting out the concrete with high-pressure water. If that is the case, then call a plumbing company that has access to a jetting rig.
Why Concrete Ends Up in Conduit
When concrete enters conduit, it is usually because the ends were not adequately sealed when the concrete was poured and some of it ended up inside the conduit. Sometimes the concrete intrusion could be from a crack in the conduit that formed from rough handling during installation or a faulty glue joint. There are plenty of other types of situations where conduits end up with a hole or crack in them that allows concrete to enter when the slab is poured.
It's hard for somebody not involved in construction to fathom how these mistakes happen. During construction, there are so many different situations that come up where somebody didn't follow the plans exactly, or misread them, things get missed, forgotten about, miscommunication occurs, and things get crossed up and mistakes happen—like conduit getting damaged during the installation and not being discovered until six months later when the electricians are trying to pull the wire.
I would say it is a rare occurrence where a construction project can go from start to finish without something going wrong somewhere. There are so many steps that involve so many different contractors, and the time is so long on the project that mistakes are bound to happen. It's easy from an outsider's perspective not to be able to understand how some of these mistakes happen in construction projects, but on the inside, living the construction life, it is easy to see how they are made, and you are not surprised when it happens.
Some examples include a hole being drilled into the conduit during construction after it is buried, or a piece of rebar driven through it by accident, or the conduit being bored through by a directional boring machine to add more conduit because of a change order (I have personally seen that one happen). The question is, when a problem comes up, what is the best way to fix it?
For example, when a bank of conduits are in a chaseway of poured concrete underneath a roadway and concrete has found its way into the conduit, the only option at that point is to remove the concrete or use another conduit if a spare is available. If a spare is not available, then removing the concrete from the conduit is now the only option other than digging it up and starting over or risking more possible damage to existing utilities by directional boring and installing a new conduit if that is possible. If the conduit is PVC, a concrete dissolver like Croc-Crete may be the only viable solution at this point.
What's Really Causing These Blockages
Understanding how concrete gets into conduit systems helps you prevent it from ever happening to begin with:
Bad Pour Coordination: If there is miscommunication between concrete crews and the general contractor, then mistakes are more likely to happen, like unsealed conduit entries, missing caps, and slurry flooding your lines during pours.
Loose Uncured Grout: Wall or slab grouting can make its way into nearby conduit runs.
Skipped Protection Steps: Conduit ends that have not been taped off during construction are likely to collect dirt, debris, water, etc. If uncured concrete dust happens to find its way into the conduit and there is moisture present, then you will end up with a hard concrete deposit that will have to be addressed before the wire can be pulled.
How to Spot a Conduit Blocked with Concrete
Any contractor who's dealt with this knows these warning signs when discovering a blocked electrical conduit:
Failure to Pull Feed Rope or Wire Bundle Through Conduit: If you are having trouble sending the pull rope through the conduit and it either won't feed or is getting hung up, or you get the pull rope through but now the wire bundle is getting hung up at a certain point and you just can't get it through the conduit, then concrete could be the culprit. Pulling the bundle of wire back out and inspecting it may show evidence of concrete. A camera inspection can verify if concrete intrusion has occurred and the location and extent of the intrusion so an educated decision can be made on how to rectify the situation.
Insulation Abraded During Pull: Cement in the conduit can damage wire insulation as the wire passes by the area where the cement intrusion has occurred. Run a Megger to test for insulation breakdown that might have occurred.
Moisture Buildup: A conduit holding water that should not be is an indicator that something could be off. If the conduit is open on both ends and there is no blockage and it's holding water, but the water can be blown out freely with compressed air (from a large diesel compressor like a 375 or 750 CFM), then it is probably just a belly in the pipe. However, if the water can't be blown out the other side of the conduit with compressed air, then the conduit could be blocked with concrete, sand, debris, or some sort of sealer.
What You Can Actually See: Use a camera with a sonde and locator to help investigate the problem. Now you can see what is going on and find out what is actually happening. That old saying, "A picture is worth a thousand words," applies here. Once the camera is in the pipe, you will be able to see what is wrong, what the blockage is, how full the pipe is, how far the blockage extends, where the blockage starts, where it ends—all this important information is needed for planning your approach for a solution. It's also a good idea to look at the ground above the area to see if anything has been recently installed that required concrete for anchoring, such as a sign or pole, as this will provide information on the situation as well.
Circuit Acting Up: If the wire bundle manages to get pulled through the conduit that contains a partial blockage created from cement intrusion or other foreign substances and the insulation is damaged, then a whole mess of problems can develop immediately or over time. If the insulation is torn and the wire exposed but not touching anything, then, depending on the voltage of the circuit, there may not be any immediate effects if no moisture is present. However, over time this exposed wire could lead to current leakage, which can cause corrosion of the wire, further degradation of the insulation, possible heat buildup, which could lead to melted wires and conduit, fire, and ultimately a direct short circuit and loss of power to the load that is powered by the circuit.
It is also possible that if the insulation is pulled back on multiple wires of opposing polarity and they are touching, then a direct short will occur once power is applied. Then, depending on the voltage and ampacity of the circuit, the effects can range from just a breaker tripping to an explosion.
Why You Need Professional-Grade Chemical Solutions
Property owners call asking, "What will break down concrete," and "Can I chip or drill out the concrete," and then they try DIY fixes that may be minimally effective or even make things worse. Chipping or drilling the concrete out of the conduit may only work if the deposit is only at the entrance of the conduit and it is straight; otherwise, drilling or chipping is not going to be a viable option.
It is common practice to try muriatic acid, and while muriatic acid is great for etching a concrete driveway to prepare for painting, it's not so great at dissolving a 3-foot-long piece of concrete that is contained in a PVC conduit. Muriatic acid is just an acid: it is not engineered to possess the attributes needed to dissolve thick concrete, and especially not in a pipe; therefore, the results are usually disappointing.
Professional concrete dissolvers like Croc-Crete are engineered specifically for this job. The chemistry targets the Portland cement binding agent calcium while leaving the PVC conduit and wire insulation alone.
Important Safety Considerations for Using a Concrete Dissolver:
- Chemical dissolvers require proper ventilation and PPE protocols
- Electrical systems must be powered down or properly isolated during treatment
- Neutralization and disposal require hazardous material handling knowledge
- Improper application can create toxic gas formations
- Electrical code compliance verification requires licensed inspection
How Contractors Actually Clear These Blockages
If you're dealing with a cement-blocked conduit project, depending on the severity, here's the approach that may work without damaging your system:
- Map Out What You're Dealing With: Use push rods, cameras, sondes, and locators if possible to figure out exactly where the blockage is. Identify the ends of the affected conduit and set up your containment boundaries before you proceed to the next step.
- Prepare Conduit: Make sure water and loose debris have been removed from the affected conduit.
- Apply the Croc-Crete Correctly: Read through and understand the instructions of the concrete dissolver. Generate a plan that will accommodate the requirements set by the instructions when applied to the affected conduit. Execute the plan carefully and methodically.
- Clean Up Thoroughly: After the project is finished, rinse and neutralize any remaining chemical residue with proper neutralizing agents, then flush with water and blow conduit dry with compressed air from a large compressor before installing new wire.
- Verify the Work: Before installing wire, inspect the conduit interior to confirm complete clearing and any damage that might be present. Test insulation integrity on existing wires, then proceed to the next step.
What Determines the Best Concrete Dissolver
The best concrete dissolver for conduit clearing has to hit specific performance marks that regular products just can't meet:
Predictable: Is consistent in its nature of dissolving concrete.
Job-Site Tough: Stays effective across normal temperature ranges.
Clean Disposal: Neutralizes to environmentally acceptable byproducts that go through standard construction waste channels.
Croc-Crete hits all these marks and is built specifically for trade use for dissolving concrete that has found its way into plumbing, PVC electrical conduit, etc. The formulation gives you predictable results, typically clearing standard 2" shower P-trap blockages in 1-3 applications, depending on the situation. For PVC electrical conduit, it cannot be readily predicted due to the wide variances in conduit layout.
The Real Numbers: Clearing vs. Replacement
When you're weighing clearing blocked electrical conduit against ripping everything out and starting over, here's what the costs actually look like:
Chemical Treatment: Professional dissolvers run $300-500 per average blocked section for a small clog in a section of 2" PVC conduit, including neutralization materials and disposal. For larger and longer electrical conduits, the cost, time spent, and difficulty can vary greatly depending on the size of the pipe and length of the slug of concrete to be dissolved, and accessibility to each end of the pipe.
Labor Hours: Clearing a deposit could need as little as 2-4 hours of tech time over 1-2 days for a small concrete deposit in a piece of 2" PVC conduit to a much longer time for larger pipe and longer deposits. Replacement? That will entirely depend on the situation. It could be as little as 8-16 hours, including demo and repair work for a simple situation, to much, much longer for a more complex situation.
Collateral Damage: Chemical clearing preserves the structure and concrete around it. Replacement means demolition and restoration, which can be very expensive and time-consuming, or may not even be an option at all in some cases.
Schedule Impact: Since chemically dissolving the concrete is less invasive, other trades may be able to keep working uninterrupted on their projects. Replacement may have far-reaching effects on major construction, which results in major setbacks that may affect all the trades and their progress.
Code Compliance: Cleared conduit keeps your original installation compliance. Replacement might trigger upgrade requirements under current NEC provisions.
Takeaway for Property Owners
Clearing blocked electrical conduit requires specialized trade knowledge, professional-grade chemicals, and proper safety protocols. Contact a licensed electrical contractor for proper assessment and resolution.
Takeaway for Contractors
Croc-Crete provides the professional-grade solution needed for safe, effective removal of concrete and its variants from PVC electrical conduit, PVC pipe in plumbing systems, and other plumbing system applications. The product is engineered specifically for trade use and delivers consistent results without conduit damage. When facing cement-blocked PVC conduit or pipes, rely on proven professional methods to restore system integrity efficiently.
To get started, place your order today, or contact us for more information.