====Choosing a lining====
'''Plastic/rubber''': <br>
In general it would appear that choosing a plastic/rubber lining is not an option in most circumstances due to combinations of fragility, expense and feasibility for welding together sheets for larger ponds. Below the pros and cons of various liners are discussed: There are five main types of liner constructions: Polyethylene, Polythylene, PVC liners, EPDM/rubber, and polypropylene. As an indication of costs, an EPDM/rubber sourced in the UK is around $6.5 per square metre not including shipping costs.
'''Choice of lining needs further consideration''':<br>
* Needs to be food grade since the water it stores is for drinking.
* Cost: Polyethylene and Polythylene liners typically cost half that of Polypropylene and EPDM. PVC and PVC-E liners are the next step up from Polyethylene
and polyethylene in terms of cost. Compared to other liners, PVC is somewhat more affordable, while being somewhat puncture resistant at the same time but in terms of durability, the typical 20-mil (i.e. 0.020") thick PVC is somewhat mediocre in terms of durability. EPDM is more expensive than Polyethylene, polyethylene, and PVC liners, but can last for up to 20 years. Polypropylene is an expensive material but can last for up to 40 years.
'''Durability''': <br>
* Polyethylene and Polythylene liners typically only last one season.
* Polyethylene will readily conform to any shape, however, it does not have the sturdiness that is required for a permanent pond liner.
* EPDM (Ethylene Propylene Diene Monomer) rubber liners are recommended for most pond installations because of their delicate balance between longevity, flexibility, affordability, and their lack of toxic plasticizers. Because EPDM liners are rubber-based, they are extremely flexible (much more so than PVC liners) - the extra flexibility of EPDM comes in handy when working with irregular folds and shelves that are commonly found in a pond. They also do not contain any plasticizers that can make the liner brittle and crack with age. A 45-mil EPDM liner can last for up to 20 years because of its natural resistance to UV, and its puncture resistance.
'''Sheet size''': <br>
* Ideally we should not have to weld sheets together in situ.
* The main advantage of polypropylene is that it comes in large sheets larger than 50’ x 100’. If you are building an extremely large pond, polypropylene may be
* 12 m2 of plastic sheet
* 3 m of PVC tube
==Costs==