Gardening adivce regarding drainage 19 March 2021 at 2:13PM in Greenfingered MoneySaving 12 replies 242 views

googlefast

Hi all

We have a really bad drainage probelm in our garden, it gets really soggy during rainy months, I've got a landscaping company coming to do "herringbone drainage trenches" which I know little about. I was wondering if anyone here has had experience with fixing gardens with drainage probelms, and drainage channels, I have very little knowledge on this issue and I'd like to make sure that this company will do a decent job.

Thank you

Alter_ego

I'd be asking where is the water from the new drains going to end up

twopenny

And where is it coming from?
Why does it have drainage problems?

googlefast

Alter_ego said:

I'd be asking where is the water from the new drains going to end up

The drainge is meant to carry the water from the front of the garden (the lowest area with biggest drainage problem) to the rear (which is higher ground), he's meant to dig the channels so that there's it's sloped downward from front to rear, he didn't say anything about installing a soakaway so I'm guessing that the water is simply meant to sink into the ground there. Would this method work?

googlefast

twopenny said:

And where is it coming from?
Why does it have drainage problems?

It's rain water that takes a really long time to sink into the ground, my understanding is that it's because of the clay soil that's common in our area.

Apodemus

Got to be impressed when someone has the b**ls to design a drainage scheme that takes water from a low-lying area to a higher one!   The potential flaws in the plan are so obvious, that they must be confident that they know what they are doing, so I think I would be tempted to trust them!    

googlefast

Apodemus said:

Got to be impressed when someone has the b**ls to design a drainage scheme that takes water from a low-lying area to a higher one!   The potential flaws in the plan are so obvious, that they must be confident that they know what they are doing, so I think I would be tempted to trust them!    

I think his idea is to make the trench deeper as it goes from low to high ground. It would have been a lot easier to connect to the mains drainage system but apparently that's against the law.

twopenny

It seems to be a regular system for bowling greens and playing fields but those are flat 
I too wondered where the water would end up, where it would drain away. Perhaps there's a gravel layer at the back.
I think the only way to ensure they do a good job is to ask what their guarantees are of it working. Do they come back and have another go if you still have a problem. Within reason obviously. 

Apodemus

twopenny said:

It seems to be a regular system for bowling greens and playing fields but those are flat. 

Yes, herring-bone systems are absolutely standard but the main spine of the system needs to lead to a drain, a soakaway or to sufficient storage to cope with short periods of wetter weather. 

If the landscaper is routing the pipes from the low-level at the front to deeper under the higher back garden, then I would imagine that they are probably putting in a perforated pipe all the way round, so that the whole line (and the gravel backfill in the trench below the pipe) acts as a linear soakaway and provides that temporary storage for downpours.   

Googlefast, you could probably do the maths on the whole thing yourself by estimating the volume of the space created in the pipe and trench, doing a percolation test in the front garden, and working out the maximum rainfall that the system would need to cope with.  I would imagine that this is what the landscaper has done (most likely he has done this "in his head" based on previous local experience).  So it all comes down to how reliable the landscaper really is - if he is good he will have the skills to pull it all off, if he's a cowboy, however...

googlefast

twopenny said:

I too wondered where the water would end up, where it would drain away. Perhaps there's a gravel layer at the back.

I think the only way to ensure they do a good job is to ask what their guarantees are of it working. Do they come back and have another go if you still have a problem. Within reason obviously. 

That's what I have concerns about, the soil material at the front and rear of the garden is the same sticky clay, so I'm not sure if it would solve the drainage problem if there's no place for the water to go. They have given me a one year warranty but I don't think that's enough. I'm going to contact them and ask for more details and maybe a longer warranty.

googlefast

Apodemus said:

twopenny said:

It seems to be a regular system for bowling greens and playing fields but those are flat. 

Yes, herring-bone systems are absolutely standard but the main spine of the system needs to lead to a drain, a soakaway or to sufficient storage to cope with short periods of wetter weather. 

If the landscaper is routing the pipes from the low-level at the front to deeper under the higher back garden, then I would imagine that they are probably putting in a perforated pipe all the way round, so that the whole line (and the gravel backfill in the trench below the pipe) acts as a linear soakaway and provides that temporary storage for downpours.   

Googlefast, you could probably do the maths on the whole thing yourself by estimating the volume of the space created in the pipe and trench, doing a percolation test in the front garden, and working out the maximum rainfall that the system would need to cope with.  I would imagine that this is what the landscaper has done (most likely he has done this "in his head" based on previous local experience).  So it all comes down to how reliable the landscaper really is - if he is good he will have the skills to pull it all off, if he's a cowboy, however...

Yes, that's what he said he's going to do, fill the trenches with shingle and add membranes, I'm guessing that he's using perforated pipes as well. Any idea what sort of warranty is standard for this type of job? He's only offered one year and it doesn't seem long enough to me really.