Soakaway/Existing drainpipe question

[keithrob91]

I'm having a 1st floor extension built in the next couple of months. I have planning permission and building regs approval. However, there is an outstanding question mark regarding the building regs because the plans showed the downpipe for the new extension going into the same drain as other existing downpipes, but, that drain actually disperses into the foul water system. The BCO said this was not allowed (separate foul and rainwater system). The plans were changed to state, that the rainwater drain location wasn't known, but worst case a soakaway could be used. This was accepted.

I don't want the soakaway as its the difference between £20 and £500 or so, plus I've not heard good things about them!

My question is this, the rainwater that would be carried by the new downpipe is currently flowing off the flat roof (that the extension will be built upon) into the existing downpipe mentioned above (going into the foul drain), therefore why can't the new downpipe that replaces the flat roof do the same. i.e. the water goes there now, why can't it after the extension is built?

As I understand it, the existing shouldn't but I bought the house with it like this and the BCO can't do anything about that.

Keith

 

[freddiemercurystwin]

Are you saying that with the new extension you are not increasing the roof area to be drained as you are building over the existing foot print? Therefore no increase in drainage? If so then you should be able to keep it the same. What has your designer done to argue the case on your behalf? You can try contacting his senior or appealing if you do not agree with his decision process. On the other hand, there is nothing wrong with soakaways if they are properly installed. Most who complain about them are where they have been poorly designed/built or have reached the end of their lifespan (about 20 years).

 

[keithrob91]

Are you saying that with the new extension you are not increasing the roof area to be drained as you are building over the existing foot print? Therefore no increase in drainage?

Exactly that, except the extension will be a pitched roof not flat, so I guess that will make it a bit bigger?

As for the soakaway itself, I've heard about them blocking up, the colour of the grass over it being different to the rest of the garden, overflowing with heavy rainfall. However, its the huge difference in cost that I really want to avoid!

Keith

 

[jeds]

As freddy says, your proposed roof is exactly the same on plan as the existing (it's exactly the same on plan - not bigger) and there will be no increased flow to the existing drain. Just tell BC the drain is existing and will remain unaltered.

 

[keithrob91]

Everybody who has seen the plans and existing arrangement agrees, so hopefully the BCO will to. One can hope

 

[tkmax]

There is increased rainfall on a pitched roof, to a factor determined by the pitch but it's unlikely to be more than an extra third of the original catchment. It's a harsh call to demand a soakaway based on that alone though.

 

[big-all]

i could be misunderstanding this

i think what he is saying is he can do nothing about the origonal but with the alterations needs to comply to pass??

 

[freddiemercurystwin]

If you get your calculators out and do the proper sums for pitched versus flat rooves then pitched would require more drainage, this is because they have more area, especially in conditions of strong wind, it is pretty petty though.

 

[mointainwalker]

I have no in-depth knowledge here at all, but isn't this governed by the same type of thinking that says if you renew an existing wall ( above a certain percentage of total ) then you have to renew it to new standards of insulation ?

It is just a way to "improve" things and wipe out irregularities -such as exist here - that are otherwise time-expired as regards enforcement.

 

[DevilDamo]

There will be an increase in surface water drainage, but not a lot. And I'm pretty sure the minor increase could be accommodated by the existing RWP.

 

[Ballysillancfc]

Unusual situation this.....if the storm water from the property was originally piped to foul sewer....was there no storm drain on the street at that time? Has one been laid since?

 

[Richard C]

I don't want the soakaway as its the difference between £20 and £500 or so, plus I've not heard good things about them!

The arguments for/against aside; are you saying your being quoted “£500 or so for a soakaway”? It will cost more than £20 but £500 is an absolute joke! There is absolutely nothing wrong with a correctly constructed soak away, it’s generally all you’re allowed to do with surface water now anyway. It matters not that you already have a surface water connection to the foul drain, new building works must comply with current regs. & if that's what LABC/water authority want, I think your stuffed.

 

[keithrob91]

Sorry to come back to this after so long, but for the purposes of 'completeness' I thought I'd get back with what happened in the end.

To cut a long story short, the Building Inspector allowed the builder to put the rainwater into the foul due to the increase in water created by the pitch being negligible. The builder did suggest a water butt, which the BI also accepted, but in the end the BI just allowed it!

As for why there wasn't/isn't a place for the surface water to go, thats a whole different story ...

Thank you to anyone who commented.

Keith