Dirt falling from under edge of inground pool

[sdk2000]

Hi ,
I am new to pool owership and the pool is 10yo. Currently seeing dirt falling from under the edge of a section of pool(Left hand side of the picture is the edge where dirt can be seen falling).What could be the reason and how do i fix this?
I have also attached a close up pic to better see the issue
Thanks,

 

[Newdude]

That open area under the coping should be mortar or grout. You can see it’s a high spot compared to the rest of the coping. It probably had too much mortar / construction adhesive when they laid it causing that cavity. Now either rainwater is funneling under the patio/coping and into the pool there, or ants are moving dirt around and the water splashing under the coping is rinsing the dirt into the pool.

You can seal it with silicone, caulk, mortar or grout. I can’t keep silicone or caulk from discoloring indoors, outside would be even worse, so I would use something cement-y Squeezed through a bag like cake icing.