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Patio and aircon drainage issues

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Patio and aircon drainage issues


I have a problem with a patio drain and hoping that someone can offer me some ideas on a fix without having to dig up the drain. The channel drain which you can see below collects rain water from the patio and also has a feed into it from the air conditioning unit in the house. At the opposite end the channel drains out to a stormwater pipe. The first problem I am having is that the stormwater drain at the opposite end is a good 20mm higher than the bottom of the drain. So the drain is holding water and once the water level goes above 20mm it drains the excess. The other problem is that the drain at the AC feed end doesn't seem to have been installed correctly and has a gap of 10mm and the water just seeps through under the patio. I can see this is happening as the grass at the edge of the patio is well watered and green compared to the rest of the lawn.


I am most concerned about the water sitting there as I have already noticed a lot of mosquitoes around the patio and this still water seems like the perfect breeding ground.


I have included some images below which highlight the problems. Is there a way I could raise up the bottom of the drain channel? Modifying the AC drain and the stormwater drain is not an option as would require lifting tiles and concrete. 


I was thinking of running a long PCV pipe from the AC drain directly into the stormwater drain pipe. But this would not solve the issue where the water has built up from rain.


Any suggestions greatly appreciated.

Drain viewDrain view

Image below shows drain from the air con unit in the house.Garden showing possible water under patioGarden showing possible water under patio

You can see there is a gap between the bottom of the channel drain and end plate. This is where water is seeping out under the patio I suspect.

AC drain pipe, gap at bottom of drain suggests source of leakAC drain pipe, gap at bottom of drain suggests source of leak

This is the storm water drain pipe at the opposite end. what the channel drain should drain into. Its a good 20mm from the bottom of the channel drain so water below this level just sits there.

Drain at opposite end that feeds into stormwater drain pipe.Drain at opposite end that feeds into stormwater drain pipe.

Bunnings Team Member
Bunnings Team Member

Re: Patio and aircon drainage issues

Hello @AdrianCartlidge


Welcome to the Bunnings Workshop community. It's fantastic to have you join us, and thank you for sharing your question about your drainage.


One way to increase the bottom level of the drain is to put in Dingo 20kg Self-Levelling Cement. I suggest filling it up to the level of the drain pipe. Once you've increased the level, I suggest covering the cement with Crommelin 1L Exterior Grade Brushable Waterproofer. The self-levelling cement will prevent water from forming a pool at the bottom of the drain and guide the water out.


Please remember to cover the drain pipes with a plastic cover and duct tape to prevent the self-levelling cement from going inside. I've drawn up an example of what it might look like once you've filled in the bottom of the drain. Please have a look and tell me what you think.


Let me call on our experienced members @Adam_W and @TedBear for their recommendations.


If you have any other questions we can help with, please let us know.





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