Knowing how to dissolve concrete in PVC pipe starts well before you reach for any product. Drain and sewer systems contain variables that are not encountered when working with electrical conduit such as connections upstream and downstream of the blockage, transitions in pipe size, sewage, scale and mineral buildup to name a few.
At Croc-Crete®, we know contractors who wasted time and money by not fully investigating and mapping the piping containing the concrete deposit and ended up spending time and money that could have been saved had the investigation been more thorough. This guide covers the diagnostic that comes first so an educated decision can be made that will allow the most appropriate and most efficient method to be executed on rectifying the problem. If concrete is in the pipe and Croc-Crete is chosen for the solution for removal, then the investigation will allow for the most efficient application of Croc-Crete that will result in the most successful outcome of removing the concrete deposit from the pipe.
Confirming It's Actually Concrete: Diagnostic Identification
In the big picture of sewer piping, a concrete blockage would be considered “a rare occurrence” when compared to what is usually causing the clog to occur in a sewer pipe. Performing a camera inspection along with using a jetter to clean out debris in the pipe is absolutely necessary for allowing the pipe to be properly inspected to be able to assess the problem and how to deal with it. Concrete, mineral deposits, hardened grease, and sewage can also hide other problems in the pipe and can also be difficult to identify while viewing through a CCTV pipe inspection camera. Assuming the blockage is something it’s not can send you down the wrong path in choosing the correct solution and this will result in frustration, time, and money needlessly spent. This is where the experience comes into play.
Start with what the camera shows if the pipe is clean and clear except for the deposit, if not then jet the pipe with medium pressure to clean it out and remove all the loose material that the pipe contains. Now take a closer look at what you are seeing inside the pipe. This is where experience becomes very important. Concrete in a drain line usually carries visible aggregate stippled through a uniform gray matrix with a flat surface that will usually have a taper to it. Finer Portland-cement products like mortar, tile grout, and floor leveling compound look similar but smoother and without visible aggregate and usually less taper. Mineral scale is rare in pvc and usually if it is present then a jetter will easily remove it from the pipe. Grease can vary in color, texture and hardness. Soft grease has the consistency of Crisco shortening and hard grease has the consistency of a bar of soap and either one will smear your camera lense making it very difficult to see. Grease can also stink to high heaven and is usually found in the kitchen line but it can also migrate to the main pipe as well. Grease can usually be jetted out of the pipe at medium pressure. The harder grease however can require max pressure and effort to remove and if the pipe is old cast iron then there is a substantial risk of the pipe breaking during the grease removal process. Roots love to grow in sewer pipe, they thrive on the nutrients in sewage so any part of the system that is not sealed completely can allow roots to find their way into sewer pipes. Roots are usually fibrous and can vary from looking like dirty wad of Ramen soup noodles to 1 inch diameter vines. When roots are found in the pipe, and depending on how they entered the pipe, they will usually be accompanied with dirt and sand. Roots in the pipe can indicate a breach in the pipe may be present somewhere or it could be from an opening in the sewer system like a cleanout cap that is missing out in the yard and is providing the roots access to grow into the pipe. The roots will need to be removed by jetting them away by using the proper head and the appropriate pressure, this way a proper assessment can be made of where the roots are coming from and how to fix the damaged pipe. This will also allow you to make the correct decision on how to address both problems in the pipe because the pipe may need to be lined to fix the breach where the roots came through, and Croc-Crete will need to be used to remove the concrete deposit, and if this can’t be done then pipe replacement might be in order. A wall collapse on pvc is usually caused from the pipe being crushed during the construction process such as being run over by a piece of heavy equipment, or if the pipe is near a tree like an Oak and as the tree grows so do the roots and the roots next to the pipe will slowly crush the pipe flat as they grow. If the pipe is crushed it will appear to be oval shaped and not round, and may or may not be fractured. If the pipe is crushed and breached then you will see the oval shape with fracture lines visible jagged edges and usually accompanied by dirt and root intrusion.
Job context is the other half of the diagnostic. If any concrete products were recently used such as a slab was poured, a shower pan was installed, tile was grouted, in the last week or two, and then the problems just started then concrete could be the problem. If after the concrete work was performed, you now have a clog that is un clearable and is breaking sewer snake cables then concrete hardened in the drain after the pour can be suspected. If no construction happened on the property involving concrete, and the system has been functioning normally then treat the call like it is a regular clog that just needs to be cleared. It is good practice before the clog is cleared to check the bathrooms and see what is being flushed down the toilet because if it is anything other than toilet paper and sewage then it should not be flushed down the pipe and this includes flushable wipes, paper towels, feminine products, ect. Once the clog is cleared, it should be collected at the cleanout if possible and inspected for items that could cause the blockage to occur “You would not believe what people will flush down a toilet…” . Once that is done and if nothing suspicious was found to cause the clog then it would be a good idea to run the camera down the pipe to check for any problems with the pipe such as roots, broken fittings, foreign objects, concrete, ect that could have caused the clog to occur and then re-occur after it has been cleared.
Mapping the Affected Drain Section
Once you've confirmed the deposit is concrete, figure out exactly where it is located in the system. A concrete deposit in a 4-inch PVC lateral under a slab will require a different process to follow when compared to a concrete deposit running through a transition from pvc to clay at the city sewer connection.
Start the mapping by opening the sewer cleanouts, and locating the vents and fixture connections and run the camera to identify the plumbing layout both upstream and downstream of the deposit. Run the camera through the affected section in both directions if you can and locate where the deposit starts and ends. Note pipe diameter at the deposit and if it changes, where it changes, and verify all of the connections and any change in pipe material along the run. Building drawings can help if you've got them but in plumbing we have found they are not absolute and can’t be trusted until their accuracy is verified. We have found that the camera with sonde and locater is the most valuable tool for obtaining accurate information on the layout and problems in the sewer system.
What you're building is a clear picture of three things: How much pipe the deposit occupies, what materials make up the pipe, and where the access points are. That picture determines how much Croc-Crete® you'll need, how you'll apply it, how you’ll contain it, and what will be involved in the removal of the dissolved concrete slurry in the pipe.
Concrete in Drain Removal: Risks to Consider in an Active System
Concrete in drain removal can be a very challenging and expensive problem to overcome…especially in a large commercial system. The systems we work in connect to occupied spaces that contain plumbing fixtures, vent stacks, shared mains, and municipal infrastructure. The correct method of concrete removal needs to be selected based on the plumbing layout and the surrounding areas that will be affected as well.
Backflow Into Occupied Space
When you're using a test ball to contain and hold a concrete dissolving liquid against a deposit for 24 to 48 hours, you need to know where the liquid will travel and if any property damage, containment, or safety issues will occur if the test ball were to fail. Sealed cleanouts, test balls downstream, and isolation of upstream and downstream fixtures are things to consider when blocking off a pipe to dissolve the concrete . Multi-story stacks raise the risk level considerably and will need the units to be blocked off in an appropriate manner and cooperation from the people and staff that are occupying the building as well.
Sewer Gas and Vent Stack Disruption
A concrete blockage usually stops liquid flow, but in certain cases it can block venting as well and this depends on where the deposit is located in relation to the plumbing system. It disrupts vent airflow which can cause erratic behavior in toilets, sinks and showers and therefore should be given the same consideration of a pipe that is flowing sewage.
Downstream System Contamination
Once a deposit breaks down into an aggregate and sand slurry, the material has to be removed. If the slurry is not removed, and is left in the pipe to find its own way out then more plumbing problems can occur from the slurry blocking the flow of sewage or the venting of gasses.
Connections to Municipal Infrastructure
If the deposit sits near the property line, your work may affect infrastructure past your point of responsibility. Know where the property line is and the easement starts and whether the utility needs notification before you start. Past the curb stop, the work may not even be yours to do.
Mixed-Material Pipe Systems
A sewer main line exit pipe leaving the building and traveling to the city main may be made of several different materials such as PVC, cast iron, and clay before it reaches the city sewer. Fortunately Croc-Crete® is safe to be used in PVC, ABS, UPVC, fiberglass, HDPE, and cast iron pipe in good condition, and works on copper with proper care.
Pre-Method Job-Scoping Checklist
Before you commit to a removal method, confirm the following:
- Pipe material and condition along the full affected section, with notes on every transition.
- Deposit profile: partial blockage versus full blockage, location, and approximate length.
- Building occupancy status and which fixtures share the affected branch or stack.
- Cleanout access at upstream and downstream points, with isolation options identified.
- Downstream destination of the line, including shared mains, lift stations, septic, or municipal connection.
- Time pressure from inspection deadlines, occupancy schedules, or trade follow-up.
- Containment plan for the slurry that will come out of the line during removal.
How to Dissolve Concrete in PVC Pipe: When the Diagnostic Points to Chemically Dissolving
When you have confirmed that a Portland-cement-based deposit is located in the PVC pipe, chemically dissolving is the right call. Since concrete is much harder and stronger than PVC, it only makes sense to dissolve it Croc-Crete instead of risking damage by trying to mechanically remove it.
Croc-Crete® dissolves the Portland cement binder in the deposit, reducing it to a loose mix of aggregate and sand you can flush, wet-vac, or hydro-jet out. It's the pipe-safe option for most cases of concrete down the drain after a recent grout pour, floor leveler spill, or bathroom remodel, provided the deposit doesn’t contain an epoxy sealer or additive.
When the Diagnostic Says "Don't Start Yet"
A few results are a signal to pause and bring the GC or owner back into the conversation before the next step is taken.
- Suspected pipe wall failure in the affected section, or any of the pipe that is connected to the sewer system relative to the removal of the concrete. Visible cracks, joint leakage, or a collapse in the line means the pipe is part of the problem. That's a pipe replacement job, or pipe lining job, and depending on the situation the pipe may or may not be a candidate for dissolving the concrete located in the pipe.
- Deposits containing epoxy or acid-resistant sealers, which Croc-Crete® won't dissolve. If the original pour included either, chemically dissolving the deposit will not be an option.
- Insufficient access to apply, contain, and remove the product safely. If you can't isolate the deposit or capture the slurry, you need another access point before starting and this may require excavating or cutting floors.
Documenting the Diagnostic for Client Records
Your CCTV footage, written notes, and photos from the diagnostic phase are part of the report. Pre- and post-work comparison provides invaluable information and protects you from billing disputes and shows the client what they paid for. Notes on pipe condition flag follow-up opportunities and protect you from being blamed for failures that were already developing in the line.
Treat documentation as a billing and liability asset, not paperwork. The diagnostic records, drawings, and videos are often the most defensible pieces of information of the job and are invaluable to prove the integrity of the work performed when something gets questioned six months later. This is especially important when you are dealing with commercial properties where building managers and head maintenance guys may leave and all that information could be lost and becomes invaluable when needed in the future.
Where Croc-Crete® Comes In
When the diagnostic report confirms chemically dissolving is the right call, Croc-Crete® is the professional-grade option for removing hardened concrete and avoiding pipe replacement in drain and sewer systems. For use by experienced contractors only.
For more product information or support, contact Croc-Crete® at 1-844-688-4814 or visit our Shop page to place your order.
Frequently Asked Questions
How do I confirm a blockage is concrete and not scale, root mass, or hardened grease?
CCTV and a jetter is the first tool of choice but in reality if a blockage has formed, more than likely a plumber or two will have been called out to run a snake to clear the clog and fail before the expense of running a camera in the pipe would even be considered. Usually when the plumber is called out, the plumber will find that the snake may bind up in a pipe with a concrete deposit since the deposit is hard and unyielding and if the plumber does not pick up on this and continues to try and clear the clog with the snake then the snake cable head may hang up on the concrete and break the snake cable or the pipe may break or wear through. Concrete carries a visible aggregate set in a uniform gray matrix with a hard flat surface. Mortar, tile grout, and floor leveling compound is very hard also and looks similar to concrete but smoother, without visible aggregate. Scale builds up in layers with color variation and is usually soft enough to be removed with a jetter or snake with the proper head. Roots are fibrous. Grease can vary in color, usually smells, is usually much softer, and will grease up on your camera cable and smear the camera lens. Job context backs it up: a recent slab pour, masonry work, or floor leveling spill in the same area as the clog suggests it could be one of these deposits.
What's the most overlooked risk when working on a concrete-blocked drain in an occupied building?
Flooding of the building due to backups and especially on a multi story building. People will continue to flush even though there are signs up indicating the sewer system is out of service. Shut off the water to the building and rent portable bathrooms for the occupants to use until the situation is under control. Also another risk is connections that were missed or were not fully verified. Contractors trace the obvious line and sometimes miss secondary ties like floor drains in mechanical rooms, or abandoned fixtures still connected to the system. It is rarely a perfect world when running a camara in a pipe and the vision is rarely ideal and it is also very possible that the line may not be passable by the camera if it is clogged with concrete and other material like sewage and toilet paper. Verify every fixture and where it ties in, and how it will affect the job.
When should I bring in the GC or utility before starting work?
Bring in the GC when work could affect plumbing downstream of the problem or fall outside of the scope of the building regulations: structural elements, shared plumbing, or finished spaces near the work. Contact the utility before any work near or past the property line, or when municipal infrastructure could be affected.
My CCTV shows concrete in PVC with a transition to cast iron downstream. Can I treat both with the same method?
Yes, if the cast iron is in good condition. Croc-Crete® is safe on both PVC and sound cast iron. If the cast iron shows deterioration that compromises the wall, that section needs its own assessment before you commit to using a concrete dissolver.
Is polymer-modified concrete handled differently from standard concrete?
What actually prevents the dissolving of the concrete is the presence of an epoxy additive or sealer that has been added to the concrete, which unfortunately Croc-Crete® can’t break down. There should be information available on the concrete when it was mixed whether it came from a bag or a concrete truck. If unsure then test a sample of the concrete and if a sample is not obtainable then go ahead and apply the first treatment and see if a reaction occurs and if so, then continue and if not then Croc-Crete will not work and another method will have to be considered.