How to repair a concrete water tank

How to repair a concrete water tank

Are you wondering how to fix a leaking cement water tank and can it even be done? Or maybe you just want to know how to seal it again?

For both questions, I’ll try my best to provide a good answer so you don’t have to look any further. The good news is that depending on the amount of damage, it can be fixed.

There is an article on this site about concrete water tanks and how long they last. The promised age that many precast cisterns have is 20-30 years.

Some even have a warranty of up to 20 years so you should check what that covers before you do anything by yourself. If your water tank is a rather new one.

If you have made the water tank yourself or don’t have a warranty, read on further. I’ll try to explain common fixes.

Repairing a concrete water tank is much like fixing any other concrete damage. You just need to keep its purpose in mind and fix it strong.

How to repair a leaking concrete water tank

How to fix leaking concrete water tank

Step 1: Before you can start concrete water storage tank repair, you need to drain it of water.

Step 2: Now depending on the tank type, you need to get some air flowing in so you don’t pass out in there. Breathing CO2 is a silent way to pass out so you have to be sure before you enter the tank that it’s safe.

Have someone else with you and warn them not to enter if you pass out so it won’t happen to them. Have some other way to get help or save yourself.

I’d get a tool for measuring the air that can warn you when it’s reaching dangerous levels. That’s what I’ve used repairing underground water tanks like water cleaning plants.

Step 3: Depending on the place, if your tank is for drinkable water, you need to order a liner for it. So you need to measure the tank and order one that fits the size and that is used for drinkable water.

If you feel it’s an annoyance or something else like that, it should also prolong the life of your water tank. At this point when it’s cracked and maybe has a little age going on for it, it’s the perfect time to do this to get some extra years out of it.

Step 4: Not that you have ordered a liner, it’s time to do some concrete water tank repairs. Proceed as you would do with other concrete cracks.

You need to take a chisel and hammer or hammer drill with a chisel bit and remove loose concrete from the crack. If the concrete is soft around the crack you should remove it if it comes off easy.

If you see more beginning cracks over there, take an angle grinder with a masonry blade and cut them like you would do a dovetail joint with wood. You can even make 1 inch deep and 1-inch wide dovetail cut so the fix has a better area to adhere to.

As you can see, when you trowel the patch in and let it cure, it will be like a piece of a puzzle that can’t come out. It’s more work than doing a square cut or V shape, but it will hold the best inside and outside.

It’s smart to do an inspection now and fix them than deal with more cracks a few years later.

Step 5: Clean the debris away and use a pressure washer to wash the cracked spot and everything else you opened up. It will let the dust off so the fixing material will adhere well to the surface of the crack. Just like we would do outside.

Step 6: Use a concrete bonding agent on the cracks if it’s the local way. Then mix hydraulic cement with water according to instructions from the manufacturer’s label. Use an electric drill and mixing paddle to mix it well.

Hydraulic cement is a popular way to fix concrete structures that deal with water. It’s used on swimming pools and drainages alike so it will work here as well.

Now, this isn’t the only way to fix concrete and some polymer products might work as well. You should consult local hardware stores about the best products if these are not available.

So use whatever product you got for water tank crack filling and remember to mix it following the manufacturer information. Use a trowel and float to make the patch smooth on the surface.

Let the product that you use dry as long as the manufacturer info says. If it says to wet it, then wet it as long as needed. It will make the cement harder.

Step 7: Clean the tank of debris again before installing the liner. The liner will be in between water and the concrete so my thought on this is that there shouldn’t be anything that breaks the surface under the liner.

Also, check how to install the liner that you’ve got. Some are for open tanks and some have to be installed for closed tanks. You need to check how to attach them to the tank.

With open tanks, they can be attached to the outer surface. With a closed tank, it has to be attached inside, to the upper part of the wall.

Note: There are also products like epoxy and polyurethane on the market that are used as a coating on the surface. This kind of thing was used when I was working at the water cleaning plant as it’s a chemical resistant solution and strong surface.

Step 8: Follow manufacturer information for installing the liner. It might involve using some adhesive product that is used on the concrete. Now this will be a challenge to do without a mess.

I’d proceed in the same fashion as when I install floors with adhesive. Half and a half.

Place the liner in place. Then remove it from another half of the tank and place the adhesive on it. After that use something to press it flat on the adhesive.

When the first half is done, we take the other half and pull it on the surface that is ready, then use adhesive on that part of the tank. After that, we press the liner on the latter half.

It’s best if the adhesive has a long working time as it might take some time for a beginner. My advice is the think it well through and only do it when you’re certain you know how it will work.

This way you won’t make any mistakes and you’ll get it done.

Step 9: After the adhesive has worked its magic, you should work on the other attaching measures. After that your concrete water tank leak repair is officially done.

Waterproof coating for concrete water tanks

This is an alternative for liners. Waterproofing concrete water tanks will protect the concrete structures from the water they are containing just like liners do.

The difference here is that the surface needs to be prepared better than with liners. Sandblasting or grinding and pressure washing all the debris away.

Depending on the product used, the application process might be a little different as well. There are epoxy, polyurethane, and cementitious coatings to begin with.

These are probably the most common ones used on the market. Depending on how it’s built, this might be something to be used as waterproofing for an underground water tank.

When it comes to water tank waterproofing methods, some of these can be spread with a paint roller while others need to be sprayed. It’s good to check the manufacturer again, they tell you how it’s supposed to be done with their product.


You should know now how to repair a concrete water tank using liners. It’s a pretty good method when your concrete starts to leak.

In this kind of situation, you should also compare how much new water tank would cost. Depending on the age and damage on the current water tank.

If the concrete is starting to feel its age and is getting soft and the rusting rebar is making some concrete spalling, it might be a better option.

If the concrete is not that old and in good shape, repairing it is a valid option. Things like this are better to be done early rather than later.

The more the crack is affected by water, the more you need to repair it. The more you need to repair it, the weaker the surroundings are.

Early intervention is always the best way to prevent damage. It will also always be cheaper.

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