Sand or Gravel for back fill around drain ?

Hello.
The other day I went to replace the concrete around the drain. It has been cracked for some time. I chiseled at the old stuff and it broke away without any effort. It was then I could see that the main body of the grid (I think it's called the gully) was surrounded with black stagnant water about 2 layers of bricks high (I have added a link to a photo)
https://s32.postimg.org/5nk0ny3l1/grid.jpg
I Sponged all the water out and now there is a large void around the body of the grid. I am not sure yet if this water is a result of water getting in through the old concrete or possibly a leak in the clay pipe. I have noticed water slowly seeping back into the void - although this could be from the water logged soil .
What would be best for filling this void and stop the water pooling? Sand or gravel? It looks as if there had been sand in there in the past. The house was built 50 years ago.

Thanks in advance

 

Thanks for your reply.
This is for waste water. Kitchen and bathroom drain into it

 

Thanks for the replies.
I did sponge all the water out of the gully and I could not see any hole at the base - it looked ok

 

If this is a leak problem would getting a new gully replaced be a costly job ? it would mean breaking through about 2 inches of concrete path to get at it.

 

Thanks for the photo.
The damage, if any, could be on that part at the back that sweeps up to meet the pipe.
If I wanted to get someone to do the job would I contact a general domestic plumber do they do this type of work or would I be looking for a drainage company ? Any indication of the types of quotes I should expect.

 

Thanks, again.
It's not my house it's my mother's - so just wanted to give her a rough idea of possible cost. I will also ponder whether it is a DIY possibility..do some reading around and have a more detailed look at the area around where the gully is situated.
Many thanks.

 

An update from my last post:
Well, I had a closer look at the area around the gully. It looked as if it was leaking low down where the neck enters the branch connection. The collar of the branch was not broken but it looked like what ever was sealing the gully into the branch (it looked like bitumen) was partly missing and I could see water slowly coming out. So I decided to break the concrete away. It soon became obvious that there was no way I was going to get the gully detached from the branch to try a reseal as there was a large dump of concrete right over the join.
https://s32.postimg.org/m9vp881vp/concrete.jpg
Also the collar on the bend connecting to the soil pipe broke away, it probably cracked when breaking the concrete - I have managed to fix a temp seal to it. Anyway I have now exposed the pipe back to the first length of straight clay pipe.
https://s31.postimg.org/fsahzz4kb/trench.jpg
I noticed a crack on top of the collar on this pipe .
So, I will now replace everything up to this first pipe, I will cut the collar off and use a rubber connector to connect the clay to the 110 mm plastic. I have a 115 mm angle grinder - will this be big enough to cut the collar off the clay pipe? If so, what would be the best type of cutting disc to use?
I'm thinking of buying all the bits from
http://www.drainagepipe.co.uk/
their prices look very good - anyone had any dealings with them?