How to install a puddle flange in concrete

How to install a puddle flange in concrete

Is there a bathroom renovation on the way and you’re wondering are puddle flanges mandatory and why do you need one? Or maybe you already have reached the conclusion you have to do it, but don’t know how?

Let us go through both of these questions so we can reach a better understanding of the subject. You do need a puddle flange on a concrete slab or wall if there is a pipe passing through it. This would be the case with pretty much every bathroom that has sewer pipes.

Now there are different kinds of puddle flanges available at the stores. There might be a plastic puddle flange meant for the bathroom floor on the shop shelf or a more flexible one that is meant to be inside the concrete and is attached on spot with metal clamping bands.

The leak control flange is usually the PVC one you see on the bathroom floors. The flexible ones can also be used in bathrooms, but have to be installed inside the bathroom concrete slab.

What is a puddle flange and are they necessary

So what is a puddle flange and why do we want one? Can’t we just let the pipes be at peace if we don’t use them that much?

The thing with sewer pipes and such is that they don’t adhere to the concrete. So water can travel on the exterior of the pipe free of obstacles.

If we have a bathroom on the second floor, you can imagine that water running at the exterior of a sewer pipe would be unpleasant. It would be unpleasant even on the first floor when I know about it.

When the bathroom floor is waterproofed, there are different solutions when it comes to the floor drains. Some puddle flange floor waste is done with the waterproofing coating while some are located inside the concrete slab.

The purpose is the same thought, we want the water to travel inside the pipe. Not on exteriors.

Now puddle flange sizes change from place to place and I don’t think it matters too much. It should be in proportion to the floor or wall. Thicker slab, bigger pipe, bigger puddle flange depending on pipe size, etc.

So as always, puddle flange dimensions should be chosen by how it’s being used. There are also metal cast puddle flange pipe sleeves if that kind of thing is necessary.

So in short, puddle flanges are necessary to stop the water from traveling uncontrollably and are required most often if you read building regulations.

Puddle flange installation in water tank might be bit different

Puddle flange installation

The installation will depend on the puddle fang type and purpose. The most typical one for homeowners would most likely be the floor drain and after that the concrete wall maybe.

Inside concrete slab installation

If the puddle flange is meant to be inside the concrete floor slab, it should be placed at the correct height. Now, this depends on the puddle flange type.

As stated before, there were multiple puddle flanges available. There were the flexible ones with metal clamping that can be set tight with a screwdriver and the PVC type.

The metal clamping ones are usually placed in the middle of the slab before it is poured. It will stay there and stop the water flow at the pipe exterior and keeps the pipe in place as well.

The pipe itself can be cut to the height it’s wanted or the puddle flange can be around the water drain piece. You have to check the manufacturer info on how to use the parts that you have.

Under concrete pour installation

Now, this can be done with the PVC kit that has the flange, base, and cap. Maybe there is a wooden floor or something else under it.

So the flange is attached to the floor. Then the base is set to the height that we want the lowest part of the floor to be. So the water will flow in it.

The puddle flange is also attached to the floor as the manufacturer instructions says. Waterproof is used on the surface before pouring the concrete. So when water comes from the surface tiles, through the joints and grout, it will not go under the flange but on top of it and into the pipe.

Before waterproofing, there is some sort of sealing square that is usually used on top of the puddle flange. Waterproof is used on the floor around the flange and on top of the flange.

Next, the square is placed on top of it. It will make the flange more waterproof and better in place.

Then the concrete, or whatever is used to make the floor, is poured and screeded so that the base is the lowest level and from the walls of the room you can get the highest level.

On top of slab or surface installation

If you install a puddle flange on top of the concrete slab or another floor, it’s another PVC puddle flange more than likely. Remember that it should be level with the floor so if it’s concrete, you will need to remove concrete around the pipe so it can be installed well.

To do this you can use a hammer drill and angle grinder for example. If this floor is made of wood you will have to use other means to remove enough of the surface to install the puddle flange nicely.

The puddle flange usually comes with screw holes as well so you can screw it on the concrete or wooden floor.

Before that, you should use some sort of adhering glue on the flange and the pipe and the concrete it’s placed on. Local hardware stores should know what to use.

After that it’s waterproof and sealing square again and after it’s dry, a coat of waterproof. This is usually how bathroom renovation goes where the pipes are already there.

The puddle flange pipe goes inside the old sewer pipe and you use glue around it so it will stick.

Puddle flange in concrete wall

Puddle flange in the concrete wall will depend on the use really. If it’s just your everyday pipe it might be done in the same fashion as the concrete floor.

A puddle flange would be placed on the middle of the wall and the metal clamping would be tightened with the screwdriver again. After that wall pours happens and the puddle flange will be tight in the middle and the pipe as well.

There are different systems for things like pools as well. The puddle flange would still be in the middle, but there would be additional reinforcement on both sides of the pool to hold it in place.

Puddle flange installation in water tank

Puddle flange for water tank might be more special as I think it’s most often metal pipes that are used. The kind you often see in the movies with holes to attach bolts in them to hold the pipes in place.

Now, this is my guess, but it would be reasonable to assume that the puddle flange is attached around the metal pipe in the same way that we do with sewer pipes. Then it’s placed in the middle of the water tank wall form before it is cast.

Then the concrete is poured and it will be there just like it would be on a bathroom floor or swimming pool wall. Metal pipes are just more durable and can handle much more useful if there is a need to remove the pipes etc.


I hope this answers how to install a puddle flange in concrete. I have to say that a lot depends on the type of puddle flange as there are different purposes.

If it’s just a pipe pass-through, it will be different than installing a puddle flange for the bathroom floor drain. The good thing is that for all of the products there will be manufacturer instructions available.

If there is not, choose a different product really. The PVC puddle flanges I’ve used the most myself during bathroom renovations.

It’s important that you install it right to avoid water damage. It needs to be attached to the sewer pipe as much as it needs to be properly installed on the bathroom floor.

Now is the waterproof under the floor pour or on top of it depends on the instructions from higher-ups for me. If the contract and engineer plans say it’s under, then it’s under.

That being said, it’s best to consult professionals for this kind of job. You don’t want any water damage on your hands when you don’t have any warranty for the job.

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