sealing the joints in clay channels

[monty28]

I HAVE RECENTLY INSTALLED SEVERAL FOUL CHAMBERS,AT THREE METRES IN DEPTH,WATER IS COMING THROUGH THE CLAY CHANNEL JOINTS,IVE GRANNO'D THEM ,IV'E TRIED JOINT SEALANT BUT THE WATER IS STILL COMING,I DID POKER THE BASE BUT THE WATER FOUND IT'S WAY THROUGH,WHT CAN I DO?DO I HAVE TO WAIT FOR A DRY SPELL OR IS THERE SOME SOLUTION?GIZZA CLUE.

[84-1093879891]

I'm not sure how you've built these chambers, so I'm not sure why water is finding it's way into the channel.

Normally, when we build a manhole, the channels are bedded directly into the 225mm thick concrete base, or, if we're using a semi-dry base concrete, then the channels will be bedded into a Class II waterproofed mortar on top of the concrete. This helps ensure a water-tight seal.

When you have water entering the channel through the joint, this suggests that the bedding and/or the base concrete is at fault. The bad news is that the MH will fail the SfA4 test requirements.

You could try using a fast-set mortar as soon as you get a dry spell, or you could try pumping in a puddle clay to seal the joints adequately while you effect a mortared joint, but it's going to be a case of trial and error to find what works best.

[monty28]

thats why your the gangerman?thanks for the info.i have built the base in the normal way,and added the channels directly,sat the first ring on and left it over night,came back on site the next day and water was present.its a real pain in the arse,but its like you say trial and error and pray for a dry spell??cheers mate.would a good strong 50 mm layer of granno seal it because im under the impression that granno is kinda water proof??am i under the wrong impression??

[84-1093879891]

Grano is waterproof, once it's set, but it's also relatively coarse-grained and so it's difficult to pack it into a channel joint to create an effective seal. Puddle clay is very, very fine-grained, with each grain like a small plate, and this makes it eminently suitable for packing into tight joiints and creating a waterproof seal.

But, clay isn't 'permanent', so we use a sand/cement mix, but use a fast-setting cement (summat like Simeon's Monoset) so that we get a sealed joint in just a few minutes, and, hopefully, the joint is water-tight long before water pressure builds up sufficiently to 'spring' the joint.

When you bedded the channel and placed the first ring, did you bed onto a semi-dry concrete or did you use a mortar? I always found that a wet Class II mortar was best for bedding the channel, as it more or less guarantees a water-tight seal.

[monty28]

tony,thanks for the recent info.i put the channels in on a semi dry concrete,but it was raining when i did it,and the hole was the only one open so alot of water found its way to the hole over night,even though i left a pump running?i'll try the monoset and fingers crossed eh?cheers mate.

[115-1093880813]

Hello and good morning, Simeon here from Ronacrete Ltd. Have seen your postings and am able to offer advice. Tony ir correct is recommending Monoset, a very fast "setting" cement mortar. Mix it with water, hand place, render, trowel, point into the gap/hole/void/joint and allow to go gain strength. Typically after 1 hour it has gone off and is doing its job. Faster versions work in minutes.

If you want to discuss please call Steve Taylor or Norman Posner in our Technical Department, 01279 638700.

Regards
Simeon Osen
Ronacrete Ltd
www.ronacrete.co.uk

[monty28]

cheers fella,i will tell my site manager asap and we will give you a call.thanks once again.