3 Inch Clay Pipe to 110mm underground Drainage and Other Qs

8 Jan 2014
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United Kingdom
Went outside “just to unblock the front downpipe” – thinking 30 min max job, hasn’t worked out like that ……

I’ve removed the hedge from the side of the house, removed edging set in who knows how much concrete and dug out PVC 68mm downpipe and Clay Pipe that was also covered in lots and lots a concrete. All right up against side of house and porch floor and running between a soil inspection chamber.

Discovered two air vents that were buried to half height at the side of the house too.

Now I’ve got a nice excavation at the side of the house, missing section of down pipe and section of clay run, remaining clay with up to 2.5” of concrete on top of it, which could continue full length. I have ideas but also questions as to how to best fix this.

1. Top of the list is, can I connect 110mm underground drainage pipe to what appears to be 3” clay? The clay diameter seems to be 3” inside and 4” outside. Plenty of those Fernco type connectors around for 4” to 4” but what do I do in this situation?

2. Initially, after clearing the first lot of roots out, our feeble 7.2 lpm hose lasted 5 minutes before backing the run up. Now having rodded and removed more roots and cleared for 4.5metres I’ve run it for 1 hour, which I calculate is 432 litres and it was still going. Will that give this a chance of working adequately? It covers approx. 8M x 6M foot print front and side roof elevations of a 3 Bedroom Semi.

3. There is obviously a decent amount of silt and sludge at the end of the run which a screw on a rod won’t pull out. Is there anything else I can do or worth doing to clear further – worth paying for a drain clearer with some equipment other than drain rods?

The first preference I initially came up with, to fix the pipe run properly, was to run new 110mm pipe out to this soakaway full length but my assessment now is that is going to be a major headache.

4. My second option was to connect the down pipe (via a gully trap) at ground level or below across to the Soil Pipe about 3m away to the left. Is that allowed on a dual system. Would it impede the soil pipe serving the upstairs bathroom?

· The house is 1920s.
· The draninage is already dual use, at other downpipe positions, the down pipe enters chambers mixed with foul water.

The end of the drain rods in the pictures shows where I have cleared to.

Thanks for the help.
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You seem to have a CI RWP that changes to black plastic as it enters the ground(?). The 4" salt glaze then takes the plastic insert pipe to a sump somewhere at the end of your driveway - have i got that right?

However, if you can keep up a continuous flow for 60 mins then it sounds like the pipe could be entering a mains drainage connection somewhere down the line. Is there any sign of a manhole near your boundary wall or on the pavement?

Do your neighbour's have combined or separate drainage?

RWP's should enter gullies so that they can be cleared without digging.

The manhole in pic 2. is draining what, from where? How deep is it?

The salt glaze is probably encased in concrete to protect it in the driveway.

If you have exposed air vents to the sub-area you should map out all the house air vents/bricks - a good flow of cross ventiltion is necessary for healthy suspended floors.

Depending on how you reply to the above then we could discuss connecting plastic to salt glaze or making a combined connection at the man hole in pic 2?
Yes pretty much. Likely originally the clay proceeded round the porch (90degree bend) and then another 90degree vertical up to the Cast down pipe. At some stage the bottom section of the down pipe and start of clay have been replaced with 68mm plastic. They rammed the 68mm plastic into what appears to have been already damaged 3" clay and proceeded to encase in a lot of concrete. This may have lasted a while but when I tackled it was all solid with fine roots.

Neighbours on both sides (one joined and one separate) have at least one RWP visibly connecting to foul.

The are 3 Inspection covers on our property, all foul. No 1 at back to No 3 on Front boundary and No 2 in the middle besides the excavation.

All positions shown on these latest photos with red line for Foul and Blue line for assumed soakaway.

Remember the hose pipe was only 7lpm so even an hour is only ~400 litres. A 1M^3 soakway would be 1000 litres and that doesn't take account of perculation. Although, I would concede what ever is in the front driveway is unlikely to be a modern installed soakaway. That makes collecting 400 litres in 60 minutes possible doesn't it?

There was no water visible in the No 3 (final) IC on the boundary even after 1 hour of hose in soakaway. So there is no chance the 3" pipe run interconnects directly to the foul line on the property.

A part of any fix, regardless of method, will be to install a bottle gully, below the down pipe - to capture debris and silt more than anything.

Detailed photos show the IC you ask about, which I have called no 2. It only has 1 junction from the soil stack on outside of house feeding 2nd floor bathroom. The line connects back to No 1 chamber at the back of the property and the outlet goes to the final IC (no 3) on the front boundary in the corner of the garden.

Airvents - 2 at front - 2 at sides and 2 the back. House is semi so other side is party wall.

The clay salt glaze is 3" inside diameter, just under 100mm outside. That is the biggest thing I am struggling with at the moment.

Hope that all helps. Thank you.

Thank you for the new pics and info.

Why a sump would be located in what seems to be the middle of the driveway would be most unusual. However, if thats where it is, and its causing no trouble so be it.

Forget about combining the front RWP with the man hole or Tee'ing in further down the line.

You need to cut the salt glaze just after the exposed hub and clean off the remaining stub. Use a 9" angle grinder with a stone disc. Stihl cutters can be dangerous.

Then use a Fernco, or similar, no-hub connector - they are freely available in all sizes for all materials in all transitions, just google or call a professional plumbing supplies.

Whether or not you leave the black plastic pipe in the salt glaze is your call on site.

FWIW: clean out the two gullies beyond IC number 1.

The green staining at the house/porch corner is splash from the porch roof.

google pics of gulley installations - it might pay you to hire a plumber/builder to connect the gully and groundwork.
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Thanks for reply and info.

I suppose keeping 4.5-5M away from house would only leave on the drive where it is or the far corner of the Lawn but that is where the foul line goes and IC no 3 is, so I guess it couldn't be put there very easily.

OK fernco was what I was thinking but didn't seem to readily come up in the size I will need for the clay - I will phone a merchant.

The 68mm black sleeve comes out. Just have left it there and use it to help plug it with plastic bags to stop debris entering whilst working.

The green staining is from that, but the source of the splashing is dropping water from main guttering above due to this blocked RWP. It was hidden by the bushes that were planted all along that boundary (now removed) so hadn't noticed it at all. The guttering only noticeably overflowed recently in very, very heavy downpours. Otherwise it has probably been tricking down the outside of RWP and also making way round the front guttering to the Neighbours RWP for discharge.

It can't be beyond semi competent DIY to get a fernco, sit in a bottle gully and bed new 110mm in some pea shingles and cover can it? The hardest bit seems to me is chipping all the concrete off the SG Clay without fracturing as I've already done that. And it's painstaking slow.

Taking on board a suggestion of plumber / builder - Is there anything I'failed to acknowledge to fix properly?

Have now looked at some gully info sheets / designs.

Was thinking a bend with access would be a good idea at the 90degree horizontal corner of the porch. It would then only need minor uncovering to rod.


Bottle gully was thinking of something like (or similar):


Thanks for time taken on this
Google the Floplast gully installation video - a rainwater adaptor, and a P-trap, and an adjustable bend with some off-cuts of 110mm pipe should get you to the salt glaze - thats if you want to use a trap.

The upstand (with the adaptor at "ground level") will allow you to drop the trap to a height compatible with the Fernco connection.

The adaptor (& a stub of RWP) can be removed for cleaning out the trap.

Or, you could use a slow bend with an rainwater adaptor, and an adjustable bend - no trap.

Dont use the Floplast bend that c/w a cap outlet - stay away from any future digging. But maybe i misunderstand you.

FWIW: dropping and bending a little drainage has foxed many a DIY'er - resulting in endless trips to the Merchants - but the idea is DIY so have a go.
My views (FWIW), given age of property, there are very few that are not on a combined drainage system. It already takes the RWP from the rear, so I'd just couple the front into the manhole and not tell anyone. You'll already be paying for rainwater disposal in your water bill so a drop more wont matter!
Agreed that most 1920's properties are on a combined system - but that wasn't my point when i inquired.

The pre-cast concrete chamber would require a much larger dig (at the corner of a house) than at present, and breaking into the benching and channel would require tools and skills that might tax a DIY'er, and prove costly if professional assistance was used.
Good point ree, maybe preferable should the OP wish to couple into the foul to break into the run from the manhole to the stack, worst case scenario, the short section from there to the stack needs to be replaced in plastic at the same time.
Appreciate both your time to help and reply.

Yes, I had (am) still considering connecting to foul, as you say I already pay for it. Although I also wanted to steer cleer of that pit (I.P. 2) if at all possible. Its all in nice condition now, it is at corner of house and at the very least I imagine I would need core drills. Also all the foul water of the property flow through it so it would not be good to go without it if I mess up.

I thought of backrunning to the vertical PVC stack. But also I suppose I could tee into what would probably be more SG from the bottom of the PVC stack to the I.P.

To be honest though, given whatever soakaway is there seems to support a decent amount of drainage, I am tempted to go with that and couple into the existing 3" SG clay fitting a bottle gulley.

I did think the access right angle connector sounded like a good idea but maybe not - is that because of root ingress. without something inline with the run I can't ever clear it without excavation and diassembly which seems more work than fitting that right angle connector with an access point.

Thanks again all.

Edit: Did look at P Traps but very long legnth. The space for a trap and then right angle bend to the existing run is very tight. The porch is only one brick 9" outside the property wall. For those reasons I though a bottle gully was far more viable.
I prefer bottle gullies for the simple reason they have access for rodding/jetting from the pot, (either remove the stopper or insert to provide direct access to the outgoing drain). P traps are old hat, rods wont go round and the jetter operator has to stick his arm into goodness knows what to get the hose started around the bend.....
Mmm. Thinking they are also a lot shorter to which gives me a chance of edit[actually running 110mm piping runs] around that right angle of the porch.

Unless I run a conventional trap or rain water trap length ways against house wall and then two 90 degree turns - seems less than ideal..

Of course if I couple to the 3" clay my fall back would be to revert to the Soil Stack or Soil Stack connection to I.P.2.

Are right angle 110mm connectors with access caps that bad to entirely dismiss that?
Went outside

1. Top of the list is, can I connect 110mm underground drainage pipe to what appears to be 3” clay? The clay diameter seems to be 3” inside and 4” outside. Plenty of those Fernco type connectors around for 4” to 4” but what do I do in this situation?

Thanks for the help.
Flexseal ( fernco) DC 115 :idea: Often they are strange things that appear to be too big - yet fit and seal fine . Got me going the first time I used one ;) . The DC 115 is the one I sized on their website
Brilliant. Looks the ticket.

I just hope once I cut the collar of the clay SG, it is not under the 100mm minimum. It is certainly close to 100mm hard to get an exact measurement until I can cut the collar. All the other pipe I removed was too damaged and bonded to concrete to measure exactly.

Edit: Based on your inspiration a Flex Seal AC4000 looks like it could be an alternative too.
I've not come across a salt glazed pipe yet that I haven't been able to connect to. Wickes usually have a rigid plastic type coupling that is designed to joint salt glazed to plastic and no fiddly jubilee clips either!

Here's one I made earlier using a Wickes coupling. View media item 82021 ;)

Or, if all else fails, look at the McAlpine DC-1, similar to a pan connector, it will fit inside the clayware, and then accept a 110mm plastic pipe in the socket at the other end.

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