Barryscotland Posted June 22, 2023 Share Posted June 22, 2023 A friend needs to add extra area to his soakaway and as I have a digger had asked me to help. his drawing shows a new 16m2 soakaway linked into the existing soakaway for sceptic tank. My worry is that where the new soakaway is going, due to the ground level difference it’s going to need to be deep an when I look in the sceptic tank the water level is 1.5m down and my understanding was that that water level is the level of the outlet to the soakaway? Is that correct? if not is there a way to figure out the pipe level from the water level or it just a case of dig to expose the pipe? Link to comment Share on other sites More sharing options...
Temp Posted June 23, 2023 Share Posted June 23, 2023 Won't you have to expose the pipe anyway to connect it to the new soakaway? Link to comment Share on other sites More sharing options...
saveasteading Posted June 23, 2023 Share Posted June 23, 2023 The outlet pipe is usually 100 to 150mm below the inlet. The change can be anywhere within, controlled by pipes or baffles. So don't assume the inside water is at outlet level but it's not far off. But are you linking a new soakaway area to the existing, or taking an extra pipe from the septic tank to the new area? Isn't the former all you need to be doing? It would be interesting to know the context. Why is it to be extended? Link to comment Share on other sites More sharing options...
crooksey Posted June 23, 2023 Share Posted June 23, 2023 16m2? Is that the size of the drainage filed being extended? Or is he wanting 16m2 of crates installing? (as thats huge). Soakaway crates are usually calculated in m3. Usually you are not allowed to mix a soakaway for rainwater to anything foul related (e.g. septic tank). As heavy rain can flood the tank etc. If for whatever reason you are, I would add a NRV from the new soakaway to the existing one, or add an NRV after the tank, before the soakaway. Link to comment Share on other sites More sharing options...
Barryscotland Posted June 23, 2023 Author Share Posted June 23, 2023 7 hours ago, Temp said: Won't you have to expose the pipe anyway to connect it to the new soakaway? Yes but if the water level is even close to the pipe level then the soakaway depth is going to be at least 2.5m down which is deeper than I can dig without digging the digger in Link to comment Share on other sites More sharing options...
Barryscotland Posted June 23, 2023 Author Share Posted June 23, 2023 2 hours ago, saveasteading said: But are you linking a new soakaway area to the existing, or taking an extra pipe from the septic tank to the new area? Isn't the former all you need to be doing? It would be interesting to know the context. Why is it to be extended? Linking a new soakaway to the existing. Area needs to be increased as house extension has increased the possible occupancy. Link to comment Share on other sites More sharing options...
Barryscotland Posted June 23, 2023 Author Share Posted June 23, 2023 43 minutes ago, crooksey said: 16m2? Is that the size of the drainage filed being extended? Or is he wanting 16m2 of crates installing? (as thats huge). Soakaway crates are usually calculated in m3. Usually you are not allowed to mix a soakaway for rainwater to anything foul related (e.g. septic tank). As heavy rain can flood the tank etc. If for whatever reason you are, I would add a NRV from the new soakaway to the existing one, or add an NRV after the tank, before the soakaway. They want an additional 16m2 drainage field. Back Flooding of the tank isn’t an issue as he’s lucky enough to have a soakaway overflow pipe to a field drain. It’s is a combined foul an rain water soakaway Link to comment Share on other sites More sharing options...
crooksey Posted June 23, 2023 Share Posted June 23, 2023 The way drainage fields usually work is they have to be level, so if the new area is much lower, it generally won't work as expected. If water level is 1.5 below ground, the outlet probably be at 1.65m below ground level. Its hard to comment more without seeing the drawings and the site, but the extension of the drain-field would need to be level with the existing. If you have overflow to a field drain, and this is allowed to stay in under the extension with building control, then I honestly don't see why they are insisting on an extension to the existing drain field? Link to comment Share on other sites More sharing options...
saveasteading Posted June 23, 2023 Share Posted June 23, 2023 Ok so no problems. I'd say just get digging, with the new soakaway on thd same level as the existing. The reason for needing it appears to be that it is a drainage field, not soakaway, and the effluent needs further treatment time in it. Link to comment Share on other sites More sharing options...
Barryscotland Posted June 23, 2023 Author Share Posted June 23, 2023 hes found the drawings and that shows the pipe at just over a meter so should only have to go down 2m which will be fine, so will get digging tonight. Link to comment Share on other sites More sharing options...
saveasteading Posted June 23, 2023 Share Posted June 23, 2023 Nice design. Outlet pipe is approx 1.5 below cover level, then shallow gradient from there. So won't reach 2m. I'm assuming you are making the connection at the start of the existing soakaway, then the new one is constructed flat. Link to comment Share on other sites More sharing options...
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