Rationalising our drainage

[jayc89]

Old house, shared mains rain/foul drainage. For some reason we also have an old septic tank added to the mix which discharges to a water culvert. All clay pipes, some of which have cracked so I need to start digging.

 

Currently looks something like this;

 

 

My plan is to make it look something like this;

 

 

(We're moving the kitchen to where the "dinning" currently is, including a new floor slab, so will run a 110mm pipe for dishwasher and sink waste, which will connect into that nearest IC.)

 

Does the plan look sensible? As it's a shared drain, I'll include traps on the rain water downpipes to avoid any smells. Do I need a couple of rodding points at each end of the runs; one before the downpipe nearest the drive and one before the SVP in the "Store"? 

[crooksey]

New rules means you cannot discharge a septic tank to a culvert, unless it ends up in a drainage field (highly unlikely), you will need to replace this with a sewage plant (and then continue to use the culvert).

 

I would route all down-pipes into pipework AFTER the sewage plant, so you don't get any issues.

 

Also I would an an NRV after the plant to if the culvert was to become blocked/overfilled in heavy rain it cant back flood it.

 

Probably not the news you wanted, but its the law now (since 2020).

[jayc89]

20 minutes ago, crooksey said:

New rules means you cannot discharge a septic tank to a culvert, unless it ends up in a drainage field (highly unlikely), you will need to replace this with a sewage plant (and then continue to use the culvert).

 

I would route all down-pipes into pipework AFTER the sewage plant, so you don't get any issues.

 

Also I would an an NRV after the plant to if the culvert was to become blocked/overfilled in heavy rain it cant back flood it.

 

Probably not the news you wanted, but its the law now (since 2020).

 

I should have been clearer - we currently have a mix of septic tank AND mains waste - no idea why because the extension uses the septic tank whereas the original part of the house is on mains waste !?

 

My plan is to do away with the septic tank altogether, fill it in, and only use the mixed mains waste drain, which is what the existing IC connects to. 

[crooksey]

In that case why not get the septic tank cleaned out and emptied, divert all gutters do it, then only have a foul sewer and use the culvert for rainwater.

 

Will also lower your water rates as you will only be paying for sewage and not rainwater.

[jayc89]

On 05/01/2024 at 14:37, crooksey said:

In that case why not get the septic tank cleaned out and emptied, divert all gutters do it, then only have a foul sewer and use the culvert for rainwater.

 

Will also lower your water rates as you will only be paying for sewage and not rainwater.

 

It's a good idea. The reason why I don't think I should do it is, the end of our road floods whenever we get a reasonable amount of rain (doesn't need to be a downpour), this doesn't affect our mains sewerage drain, so I'm assuming it's the water culvert backing up. Trying to push all our rainwater through it too will likely only make things worse and with us having an 1850's property, that are more susceptible to damp, I really don't want to risk surface water pooling around the perimeter of the house. 

Perhaps the septic tank would act as some sort of buffer to this, but with the extremes we're starting to see, and will likely continue to see, it's a complexity I don't think I need right now.