Completely normal, blocks arent water tight. The 'problem' arises if you have dug into the normal water table, then the site may flood when not pumped out. If it does flood that in its self isnt a problem or a disaster however it may complicate lining.
The bottom of my pond is 2ft below the average water table and flooded every night during the build, I ended up building a sump in the stie so that I could pump the site out.
If you are below the water table then:-
If you are going to glass fibre line, check with the glasser whether or not they will be able to glass it, some may say no. I thought that was the rule but Matt Williams, who can be found on Yorkshire koi, said he could have glassed mine, ho hum.
If you are using sheet liner anchored to a bottom drain etc, you need to ensure that, for the odd occasion that you might just want to empty the pond, you can lower the local water table to below the water level in the pond and or below the bottom of the pond. If you cannot do this and attempt to empty the pond too below the water table then the sheet liner will "balloon" and may tear around the BD.
In my case I have no BD, its a goldfish pond but I now wish I had put a BD in, BUT I use polystyrene underlay and would be in deep deep deep doodoo if the liner ever lifted/ballooned and the polystyrene shifted, I twigged this just before I lined the pond and was able to add a suction line running from the now lidded site sump which sits under the pond liner to the outside world. Using a black and decker drill pump connected to this suction line I can, if needs be, drain/lower the local water table and keep ahead of seepage for a short period. I have used it twice in three years, once whilst actually seating the deep section of the liner and the 2nd time whilst shifting the liner a bit.
The above also implies that, in a sheet liner pond, the pond level should always be above the water table. My highest water table in the area of the pond is a surface flood so my pond is semi raised. I have never had a liner balloon.
Posted on Aug 13, 2005, 5:20 PM from IP address 84.67.34.97