Posts for heavy gates sagging

[asdf345]

We have a pair of 6ft gates (4ft high) on 6x6 posts that were put in for us last year. We have now discovered the gates are dropping in the centre due to the posts sagging inwards. We cannot contact the original tradesman and had another come around to quote to repair them. He told us that the problem was due to the posts being softwood and needed to be replaced, but he never came back with a quote (story of our lives), so we're left with the problem of sorting it ourselves. Having dug out the posts they seem to have been set in deep enough (about 3ft) and with sufficient concrete. Is it right that the posts being made of softwood could in itself be the cause (it doesn't make sense to me, maybe someone could explain?). In addition, the bottom of the post holes have about 6 inches of water in them, so not sure if that would affect the strength (there's no evidence of rotting in the posts). Could someone please advise us what to do?

Thanks very much

[tradeaway]

people often underestimate the leverage that weighty gates have on a gate post.

this means that the concrete foundations are often too weak.

it is not unusual to concrete-in an upright r.s.j., deep into the ground, and weld some hinges to the girder. this would be clad with bricks.

i doubt that the presence of hard or soft wood is relevant in this case. its construction is simply not 'man' enough for the job