shower drain replacement

[Wayneos]

How do I replace a shower drain with a 100 mm2 drain in a concrete floor?

 

[MitchellMc]

Welcome to the Bunnings Workshop community @Wayneos. It's amazing to have you join us, and many thanks for your question about installing a shower drain.
 

In showers set into a concrete slab, the drain body is normally cast into the slab or into a screed layer above the slab, with a waterproofing membrane underneath that allows water to flow into a puddle flange beneath the drain. 

To physically replace a shower drain in this situation, the existing drain has to be cut and broken out of the concrete. That usually means using an angle grinder to cut a neat square around the drain, then carefully chiselling or jackhammering down until the drain body and puddle flange are exposed. At that point, you also have to be very careful not to damage the waste pipe below, as repairs there can escalate quickly.

The bigger issue is the waterproofing. The membrane below the screed is tied into the existing puddle flange. Once that is disturbed, the waterproofing is compromised. To correctly install a new drain, you would need to expose enough area to re-form the membrane into the new drain’s puddle flange, then re-screed around it to the correct height so the finished tiles sit flush with the new grate. That membrane work must be done correctly or the shower will leak into the slab.

Because of this, replacing a shower drain in a concrete floor is usually a partial shower rebuild rather than a minor repair. If the goal is cosmetic, it’s worth checking whether the existing drain can accept a replacement grate instead, as that avoids disturbing the membrane altogether.

If the drain itself must be replaced, this is one of those jobs where speaking to a tiler or licensed waterproofing professional first is strongly recommended. They can confirm how the membrane is configured, whether the drain can be adapted, and what scope of demolition and reinstatement is required to do it properly and compliantly.

Please let me know if you have any questions.

Mitchell
 

[MikeTNZ]

Hi @Wayneos, Welcome to Bunnings Workshop, it's great to have you here.

What is the reason for the replacement of the drain?

From your picture, you can see a definite square around the drain port itself, you can try one of two things here, the drain grille itself should unscrew (bearing in mind that it might be Left-hand thread, as in in you turn it clockwise to unscrew it).

Failing that, what I would do is get a 5 inch angle grinder, with a masonry blade and cut around that lower section of the floor around the drain itself and try and gently break up the concrete work around the drain grille, this can be done with multiple cuts closer to the grille itself, these wouldn't need to be that deep, what you're trying to achieve is weaken the concrete enough that it will break away without needing to use hammers and other such forceful tools, which could cause the PVC drain-work below to split or break.  

If you require further advice, please by all means let us know by posting below, we are here to help. 

Cheers,

Mike T.