You can water the plants but may need to re apply the pellets afterwards.

Hi, I usually water,if needed, just before sunset,so the water is allowed to soak in, without getting dried up by the sun, when you water give everything a good soak, not just a wetting,this allows the water to get down deeper into the soil, and the roots of the plants follow the moisture, which if you have just wet the soil will be near the surface, thus preventing the roots going deep.
Watering will not detract from the effectiveness of the slug pellets, they are made to last quite a while even if it rains every day, Derek.

Depends which sort you have Derek. It often tells you on the pack.

Yes, some of them don't usually last more than 1 shower. Personally I would have Watered first, just as Derek has advised then apply the pellets. Remember don't go over board with them or you'll attract every slug and snail in the vicinity. If and when I used them, I use no more that half a dozen per plant.

Hi, theones I buy, ( can't remember the name) last about 2 weeks, even if it rains.
You should aim to have the pellets spaced about 4 inches apart each way, Derek.

Those sound like the ones I use too Derek. They are a bit more expensive but as they last longer, you save in the long run!