A drain blocked with concrete

How to remove concrete from drain pipes

When I first read the brief for this article I thought the editor was having a lend of me. Clearing concrete from drain pipes? Who'd be stupid enough to put concrete down a drain, I wondered. But turns out the practice is not as unusual as one would think.

Getting concrete down drains is not only very simple but remarkably common. Regularly washing cement or other building compounds from tools, clothes and bodies into household plumbing fixtures is obviously a convenient way to go. But when you find yourself standing in a puddle of murky water because the buildup of concrete in the shower drain has blocked the pipe, you'll wish you'd made the effort to wash off outside.

We talked to some long-time plumbers about their experiences of drains blocked with concrete and some methods of removal they've seen tried. This article also touches on some of the ways concrete finds its way into household drains in the first place and what you can do to get it out and keep it out.

Is it OK to have concrete in drains?

Definitely not! Despite what some will try to tell you, concrete can easily block and even crack household pipes and should always be kept out of drains. Once particles settle and solidify (particularly in dry areas of pipe-like bends and corners) they stick to the walls, reduce flow and trap other matter. This can result in major blockages and costly repairs.

Many home renovators and professional tradespeople seem to think no harm will come from a bit of cement dust or tiler's grout being washed down the drain. And most likely there won't. Not that night. But over time build-ups can occur and the property owner will have a very difficult problem to rectify. One common problem is when new floors are being laid in wet areas and a self-leveler is used. Excess materials are often 'accidentally' dropped into the floor or shower grates and cause pipe blockages over time.

And then there are those who do know that putting concrete down drains will damage the pipes, but figure if no-one's watching they can get away with it. By the time things block up, they'll be long gone and proof or compensation will be impossible.

Put simply, the concrete and building products which find their way into drains are the results of ignorance, laziness or complete disregard.

Ways to clear concrete from drains

But if it's too late and you already have concrete in shower drains or sewer pipes don't despair. Depending on the severity of the blockage, the following removal strategies have been known to do the trick in many cases, and are worth considering before spending thousands on new pipes.

1. Flush

If the cement has accidentally (and recently) been put into a drain flushing it with plenty of water may be a simple but effective fix. Count your lucky stars if it works, and you will only really be moving the cement products to another section of the overall pipe network, but hopefully, it will remain saturated enough to not form into a hard mass.

2. CCTV inspection and high-pressure jet blasting

If it's too late and concrete has already hardened and blocked pipes, the best course of action is to have a CCTV inspection to ascertain its location and size. After that, you should arrange for a cleanout with a high-pressure jet blaster. Whilst it is possible to hire equipment and try to get the job done yourself, there are issues such as damage you may cause to the equipment or your own pipes if you have not been fully trained in its use. The high-pressure water jet equipment that professionals use have the power required to remove the concrete from your drain and generally requires nationally recognised competency-based training. If you try to do the job yourself, there is also no warranty or insurance upon which you can claim.

Professional drain cleaners have the most powerful equipment for this and are experienced in using the tools to achieve optimum results.

3. Mechanical tools

Again, use of mechanical tools such as augers (or plumbing snakes) is usually best left to professional drain cleaners or those who have experience or training. As with the jet blaster, hire costs, wasted time and the risk of damage to the hired equipment or your pipes often mean there is little advantage in trying to do the job yourself.

An auger simply breaks up dried concrete and allows it to be flushed away. A jet blaster may also be needed to remove larger lumps of concrete. However, you will need to ensure the auger is long enough to reach the blockage. Once again, this may require a CCTV inspection to be carried out. If you engage a professional drain cleaner they will often have all these items of equipment and sometimes offer package prices for the inspection and the cleanout which make the cost and hassle of DIY less attractive.

Common problems with this technique include:

  • Getting the tool to the concrete blockage if the pipeline has multiple bends
  • Damage to the host pipe when attempting to break and remove the concrete.

4. Biodegradable, cement-softening products

There are a number of biodegradable commercial products that work to soften concrete and mortar. Whilst these products alone may not completely clear a drain blocked with concrete when used in conjunction with a jet blaster they can be helpful in getting things moving again. Obviously the concrete or cement will only be moved further down the system, but again it is hoped that it remains diluted sufficiently to not re-harden. Visit your local hardware store or go online to see products available.

5. Acid

Concrete does dissolve in acid however this can be a VERY risky strategy particularly for those who have not been trained in the method. Concrete is a mixture of cement, gravel, sand and water and the acid attacks the limestone in the cement to break it down.

Risks associated with using acid:

Using any acid products should only be done with extreme caution and it is recommended that only professionals working outdoors use this approach.

There are also some pipe materials which can be damaged by using acid (such as ductile iron or concrete), so you will need to know what the entire pipe system is made of before commencing. Even if pipes are made of PVC there can be concrete or mortar-based foundations or joins that may be damaged by the acid. Again, a complete CCTV pipe inspection will provide you with this information.

Limitations of using acid:

Acid is no miracle fix. Chemicals will only work on the surface of the blockage. This means for large blockages you'll have to keep pouring it in, letting it stand, clearing the softened mass (perhaps even scooping it out if it is near the entry) and then starting again from scratch. If you don't use a biodegradable acid you can damage your pipes and the environment, particularly if you try to speed up the process with a stronger concentration than recommended (not advised). A too-strong concentration can also transform the blockage into a large clog which itself is hard to move, and slows the overall rate of dissolution.

How to keep drain pipes clear of concrete

If you're renovating or having any work done on your house, take the proactive approach and read our article, 'Cement, grout and glue in pipes: A recipe for disaster'. It contains some useful tips to keep contractors honest and ammunition for when your other half tries to claim there's nothing wrong with cleaning up the tools in the laundry sink.

When drain clearing is not enough

Sometimes drains blocked with concrete are so clogged even professional clearing fails. Build-ups of concrete or other building materials can also put so much pressure on pipes, cracks or ruptures occur. Finally, powerful jet blasters, augers or other hydraulic tools might remove the concrete but also severely damaged the pipe.

In these cases, homeowners will need to consider whether to reline or replace the pipes.

A comparison table on the advantages and disadvantages of relining and replacement will help you decide which approach is right for you. Or, if you'd like more information about finding a local drain specialist you can contact us.