Am putting in a dock. I've been told not to set the poles in cement under water. It was saaid the cement reacts with the treaated lumber and rots the poles. Is this true? Shirley

Concrete is commonly used to set the pilings. The biggest problem is getting the concrete through the water. Make sure you use the proper retention factor for the wood treatment. Many companies will "jet" the piling by using high pressure water to bore a hole. By the way, how deep a piling are we talking?

Concrete is commonly used to set the pilings. The biggest problem is getting the concrete through the water. Make sure you use the proper retention factor for the wood treatment. Many companies will "jet" the piling by using high pressure water to bore a hole. By the way, how deep a piling are we talking?

The posts are 4x4x8; sunk 2 feet in a drained lake bed. Lake will be filling back up with water probably by Thanksgiving if we get enough rain. Also spring fed.

By the way, what is a "retention factor"?
The posts are 4x4x8; sunk 2 feet into a drained lake bed. Lake will be filling up probably by Thanksgiving. According to how much rain we get; also spring fed.

Not all treated lumber is the same. Most of what you see at the box stores is only rted for exposure to the eliments and is not OK to touch the ground or water. Be sure touse the right lumber with the right rating. Pressure Treated Wood - Its Uses, Limitations and Safety Considerations from the Natural Handyman home repair and do it yourself website (http://www.naturalhandyman.com/iip/infxtra/infpre.html)

Retention factor is the amount of preservative per cubic foot of wood. Do not use the standard 4X4 from the big stores. Get a post with a retention factor of 1.0 or thereabouts If you are near any marina, they can direct you to the right supply. Depending on the length of the overall post, 2 ft. may not be enough, particularly if the ground isn't firm. How long is the post and how deep will the water be? I'd put 1/3 of the length of the post in the ground, open the hole to 12-16 inches and pour quickcrete, mixed or dry into the hole all the way to the top of the hole. For increased stability, "X" brace the posts. Hope this helps, we've put a lot of posts in water and followed these guidelines.