We just got a vinyl in ground pool and have noticed that the cut line between each coping stone are irregular from 1/8" to 1/4" and the polymeric sand is eroding every time the deck gets wet. The installer said that he could only use polymeric sand or caulking and the caulking won't match (coping is a Unilock concrete paver in light grey when dry, dark when wet). Unilock said he should have used mortar not polymeric sand but the installer said he would have to have set the pavers in mortar to use it between the grout lines. If he uses mortar now, it will crack. . There is an overhang and I can see that the sand is slipping away. It is also soft to the touch where the "grout" lines are widest. Installer said he does this all the time. We are withhold a small part of the final payment due to some other unresolved issues (other than the coping) which he was coming this week to address but now I think we are going to have to ask him to reinstall the coping.

I am in zone 5, Ontario Canada and will only be able to use the pool from May to October, if we are lucky enough to have mild seasonal changes.

Update:

Met with our installer who suggests that we caulk underneath the coping and it's face to keep the sand in. I think this is a stop gap solution and this is going to be a problem for us going forward, long after the warranty ends. Another company said they need to grind out the sand and install mortar but my company completely dismissed this. I asked them to contact the manufacturer and his answer was that he didn't care what they had to say. In desperate need of any suggestions or advise.

Thanks!