Concrete Blocking Cellar Drain

[John Peden]

My Victorian terrace has a drain in the cellar that became blocked recently. We're not putting much into it (washing machine, condenser dryer, condensing boiler) but at some point in the house's long history, some moron has poured a load of cement down the drain.

A plumber was able to unblock the drain today but the pictures show the issue:

I'd break this up with a hammer and chisel but the drain isn't easy to access:

Here you can see 40mm pipe from the boiler and the washing machine/dryer. The hole is around 500mm x 400mm in size. The drain is positioned around 400mm from the entrance.

Breaking up the cement by hand is a possibility but will be very difficult to get in there and swing a hammer. Are there any chemical options that would go to work on the cement without totally wrecking the drain?

How much would I be looking at to replace something like this? At some point in the next 5-10 years, we'd like to renovate the cellar and turn it into habitable space anyway so I have no interest in spending a massive amount to get it fixed.

 

[JohnD]

Are there any chemical options that would go to work on the cement without totally wrecking the drain?

the condensate from the boiler will eventually degrade it into sand and pebbles, especially if you can avoid diluting it with other water, but this will take years.

I wonder if you could get at it from the outside of the house?

 

[Tigercubrider]

I can only see one image but how about a very long SDS drill bit?

 

[Lower]

Might be worth pouring some brick acid down there. it should react with the cement in the concrete without affecting the salt glaze.

The danger of trying to break it up is that you break the pipe as well.

 

[John Peden]

I wonder if you could get at it from the outside of the house?

Not easily. The drain sits around 1.5m below ground which is covered in decking.

I can only see one image but how about a very long SDS drill bit?

Yeah, thinking of giving this a go but space is tight and it'd be a squeeze getting the drill bit in there, ensuring it hit the cement and protecting the drain in the process.

Might be worth pouring some brick acid down there

Any suggestion on the volume of brick acid to go with?

 

[Lower]

Dry the trap out and pour in enough brick acid to cover the surface of the cement with a thin layer. Leave it for a few hours and the see if it’s loosened the surface of the concrete. It’ll probably take a good few goes to dissolve a substantial amount of the concrete and you’ll have to keep flushing away the loose sand and gravel.

 

[John Peden]

Dry the trap out and pour in enough brick acid to cover the surface of the cement with a thin layer. Leave it for a few hours and the see if it’s loosened the surface of the concrete. It’ll probably take a good few goes to dissolve a substantial amount of the concrete and you’ll have to keep flushing away the loose sand and gravel.

That's great. I'll give that a whirl.

 

[dilalio]

Get a product called Disclean.

 

[JohnD]

(boiler condensate is acidic, that's why it attacks cement and limestone. But it is no stronger than tomato juice, so quite slow-working. I've seen it damage a concrete path, but I don't know how long it takes. With luck, somebody will)

 

[Ian H]

I can only see you first picture, i’d use a flat screwdriver to break it up and lever it out.

To replace it wouldn’t be hard. What’s surrounding it? Stone slabs?

 

[John Peden]

(boiler condensate is acidic, that's why it attacks cement and limestone. But it is no stronger than tomato juice, so quite slow-working. I've seen it damage a concrete path, but I don't know how long it takes. With luck, somebody will)

Interesting you say that as the exhaust flue drips onto our decking and has effectively acid cleaned a patch directly below it. It's probably taken 3/4 months to strip a bit of moss from the decking and bleach a small patch of wood so I would guess it'd take decades to do much damage to cement.

I’ve put a bucket underneath to save the decking.

 

[John Peden]

I can only see you first picture, i’d use a flat screwdriver to break it up and lever it out.

To replace it wouldn’t be hard. What’s surrounding it? Stone slabs?

Access is incredibly limited. You can't actually see that cement block without a camera or mirror as the drain is set back around 50cm through a small opening approx 50cm x 50cm in size. Even then, the cement block probably sits around 30cm down from the opening of the drain so all-in-all, it's a right bastard to get to!

 

[Ian H]

Ah, I can’t see your other pictures, just the first one.

By the sounds of it I would dig a trench from the room to the back of the gully, pull the gully out, fit a new one closer to you with a length of pipe between the old clay and new gully.

 

[John Peden]

Ah, I can’t see your other pictures, just the first one.

By the sounds of it I would dig a trench from the room to the back of the gully, pull the gully out, fit a new one closer to you with a length of pipe between the old clay and new gully.

That's a sensible idea but a big job. The cellar floor is cement and it would involve removing brickwork. We'd like to renovate the cellar and convert it into habitable space in the next 5-10 years so if I can get by until then it would be much preferred!

 

[Ian H]

Could you post your other pictures again?