Shed Drainage to Sewer

[Namtip]

Hi all, I'm building a large shed/workshop/man cave in my back garden (I only moved in over winter). My garden slopes down on a slight incline away from the house (which is good in my opinion), but 3/4 down it raised back up so that in the wet winter it flooded in the middle (Sussex clay ). Problem is, this is where I want to site my shed.

During these cold wet months I excavated out the last 1/4 of the garden so that the incline went all the way to the back of the garden. I then dug a pit and sunk an old rainwater barrel so that the opening was just below the surface. I popped in a water pump with the outlet running back up the garden and along the side fence where there is a manhole that collects wastewater from my house, and my neighbours each side (yes, I saw some nasty things while doing this ).

Hey presto, dryish garden for the rest of the winter! My flooded neighbours looked on enviously

Fast forward to now, I have put the concrete in and laid the blocks in a block-pier foundation (a square grid of 9 piers) on which will rest bearers and joists etc. However, before I do that, I need to do something more permanent with the drainage. My plan is to bury the 40mm waste pipe under the shed within a bedded 110mm drainage pipe serving as protective tunnel buried in a trench under the shed, taking the water from the pump (located behind future shed) and piping it under and out the front where I will then be able to take it (underground still) to the sewer.

Here's a bird's eye plan:

Here's a profile view:

My questions to you:

1. Am I doing anything wrong here, or have I overlooked anything?
2. How would I go about connecting to the main sewer - drill through the side?
3. This will be for rainwater (i.e. surface run-off water), as well as grey water from a sink which will be inside the shed. Should I just aim the sink drain at the barrel in the ground?
4. The barrel is perforated. Was that wise considering I want to potentially empty a sink into it? (I'm thinking surface pollution etc. if I'm washing an oily motorbike engine down )

Some photos for perspective:

Trench running between block piers:

Picture of the barrel (pump removed):

Hope you can help!!!

 

[dal5band]

A few points but only my opinion as i'm no expert :
1 Rainwater is not supposed to go down the sewer. Rainwater should go down into the earth i.e soakaway or down a rainwater drainage system if there is one in you locality.
2 Waste water must go down a sewer so as not to pollute the land
3 Any shared sewer is the responsibility of the local water company , even on private land. So you need their permission to muck around in the manhole. However you can connect to your sewer pipe upstream of the manhole.

 

[JohnD]

1 Rainwater is not supposed to go down the sewer.

local practice varies.

But this is groundwater. Which is not allowed into sewers.

 

[big-all]

yes your not allowed to drain to other than on your land without special permission[an exemption]

 

[Namtip]

Thanks for your replies everyone. To summarise what you're all saying:

It appears there are 3 types of drainage to consider in my build:

1. Rainwater - water that falls on roof and into guttering:
   It's infeasible to connect this to my house's rainwater system due to the gradient and the distance. I will therefore probably have a barrel to collect and reuse this once all built.
   
   
2. Groundwater - water that has fallen onto land and is either flowing on the surface or is absorbed and is either part of the water table or on its way there.
   I have identified this as a potential problem in my build during the wettest months, however
   

   this is groundwater. Which is not allowed into sewers.

   and
   

   your not allowed to drain to other than on your land without special permission

   so maybe I could keep the sump/pump system but only use as an extreme measure and not make it a permanent installation. I can still bury a 110mm pipe in a trench under the shed - but this will serve as a tunnel where I can feed a removable flexible pipe to the pump, and then remove when not needed.
   
   
3. Grey water - water from internal sinks/washbasins/showers baths etc.
   

   2 Waste water must go down a sewer so as not to pollute the land
   Any shared sewer is the responsibility of the local water company , even on private land. So you need their permission to muck around in the manhole. However you can connect to your sewer pipe upstream of the manhole.

   I have another manhole further away from the shed nearer the house where a later side extension with toilet was added in '95 and connects to the original sewage from the house. The manhole was built with the extension and is detailed on the architect's plans. Even though it is further from the shed, I think there may just be enough of a run to join directly from the shed to this manhole. It seems I can fiddle around with this manhole to my liking as it is mine, and not need any special permission?
   

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