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Hello community!
I am planning some drainage improvements in my yard of my new property and would love some ideas on how to do this trench drain better.. It is leaking at segment joints (every 1m) into my sub-deck area causing some moisture issues internally (slope of entire backyard + under deck is towards dwelling). I am also going to do a subsoil drain to handle the under the surface water, but tackling the overland flow first...
My observations of the issues with it so far:
* the drain is made up of 1m pieces of https://www.bunnings.com.au/everhard-1m-easydrain-polymer-grate-and-channel_p4770206, clicked together every 1m;
* drain drain is not installed in concrete, rather fastened to deck joists;
* the fall of many of the 1m segments was in the opposite direction of where it needs to be;
* there was a buildup of sediment in the drain and lots of water pooling during rain, likely due to incorrect fall + sediment buildup;
* the joins between the segments looked deformed (like a V shape), likely due to no concrete in installation;
* the grates over the top were too wide for the channel body, also likely due to no concrete in installation.
It seems that the trench drain is an effective (and required in order to catch overland flow from yard and multiple retaining walls) drain, but because of being right up against the deck, installing it with concrete is tricky, but I do need to replace it. I think without concrete it got bullied by the surrounding soil over time. I am also unsure how to make the correct fall (1:100) look visually ok - the deck length is 5.5m, and the height difference of the drain of 5.5cm from left to right will be easily visible.
Some ideas I had:
* try a similar installation approach but with a stainless steel grate, which might be less prone to buckling inwards, but I feel it may still get pushed up by the soil;
* remove some decking planks and do the concrete anyway;
* bring the drain away from deck by 50mm, to allow for the concrete to be on both sides of the trench (concrete would sit right up against deck, but then no soil behind it really)
Is there a way to make a trench drain work in this scenario? How do people with similar slopes finish their deck? Should I maybe divert the downpipes to a LPOD by running some PVC, delete the channel drain entirely and hope the subsoil drain (which will be 600mm deep by 300mm wide, top layer of decorative pebbles) catches everything and doesn't let anything slip under the deck?
TYIA
Denis
Good evening @Dave-1 , my apologies for late reply.
You make an excellent point re: plumbing away from house. There is actually a stormwater pipe connected to the end of the grate and that is discharging downstream of the house appropriately. I've outlined the pipe in orange (it's otherwise impossible to see as it's painted the same color as timber under the deck):
Cheers,
Denis
Hello @denisl
Let me tag @Dave-1 as well to make them aware of your question. I imagine that Dave was referring to a gap perhaps between the proposed agi-pipe drain and the deck. However, I'm not sure how big a gap Dave-1 was going to recommend.
If you need further assistance, please let us know.
Eric
Good Evening @denisl
Sounds like you have been stepping through the same thought process as we all have 
Time plus ideas really help sort things. For my preference with drainage I like a "dead mans sytem" something that keeps on working with no human intervention, such as the agi pipe and gravel. Grab that sketch book, and take a seat at a cafe and sketch out the pathways the water flows down and across your property. I need to do that with my ideas for my back yard as well.
Dave
Good evening @Dave-1 ,
Yes absolutely right! Thank you for your insight with my project and good luck with yours
Cheers,
Denis
