re-lining pond

I have a polythene lined pond,holding about a thousand gallons,well established,without pumps,etc.It is about four years old now,and we have some healthy fish(which breed) despite the absence of pumps and filters.Frogs,dragonflies,etc.abound.It is a bit green in the summer months,and barley straw helps a bit.However-I suspect a slight leak and would like to re-line it with the minimum of destructive fuss.Has anyone re-lined a pond?Draining it would be next to impossible-I would ideally like to clean it up as much as pos with a vac and then try to work the new lining in somehow.I can house the fish etc.in a small holding pond temporarily.

 

Sure it�s a leak and not just evaporation ?.
If a leak then you could allow it to continue until the water level stops dropping then go around the top of the water level to find the cause of the leak. There are kits you can get to repair punctures. If the liner is near the end of its life span then the best method is to save as much old water as possible. Bag some fill an old bath, paddling pool, buy some cheap plastic off the roll and make a temporary raised holding area for the water and plants etc. Borrow an old pump to drain the water into the temporary holding containers. Remove or heavily puncture the old liner as if left in place water will get between the 2 liners and if there is nowhere for it to drain away to the upper liner can start to rise or move away from the side walls of the pond. The pressure can cause a tear. Once in place refill the pond with the old water and then over a period of a week or so slowly add fresh or even better rain water if possible to raise it to the original level. The important thing is not to add too much tap water at once as the chlorine and in some areas high nitrates can cause problems.

 

Some good thoughts-thanks very much.