How to recognise a quality polyethylene rainwater tank
1. Polyethylene rainwater tanks comes in many different shapes, colours, heights and sizes. Some are great for under the eaves, under decking, under the floor of a house. Some are specifically designed to be buried in the ground totally out of sight and freeing up the yard. Some have corrugated look, some are straight walled, some resemble brick walls. Some have special windows for strength (some remind me of puffed quilts)
2. Polyethylene is recommended for contact with food & water. It does not leach chemicals into your water. Fibreglass can break down & colorbond steel can rust. Bags & liners can be pierced.
3. Polyethylene is more flexible, relatively lightweight & portable.
4. It is recyclable; though only buy tanks made with virgin plastic. If it has 2 colours or layers then the outside is most likely not virgin plastic and is considerably weaker in structure and is not recommended for contact with food & water.
5. What is the safety factor of the tank you are interested in? The higher the number the stronger the tank. 1 is when the tank is only just strong enough to hold the water when full without bursting. Many only make their tanks to 1.5 times the safety factor. Coastline Plastics are quality manufacturers & their tanks have a minimum standard of 3.5 safety factor. (Which is why they have never had to replace a tank in over 33 years of making tanks) If it has straps around it then it is not strong enough in the original design. (plus the straps are usually made of steel & will rust in time, even stainless steel.)
6. The weight of the tank is an indicator but only in comparisons of tanks of similar size and design. Consider a couple of examples:
· A/. A corrugated look poly tank maybe the same weight but the walls are thinner, because there is more surface area to cover than a in straight wall tank of the same size. Corrugations (like a steel roof) work to make a flat sheet stronger but not in a round tank. (Plus it is an old fashioned look in my opinion).
· B/. A wall liner (or slim line) tank should be heavier than a round tank of the same capacity. (Round tanks are naturally stronger than straight wall tanks as water wants to push out and the pressure is evenly distributed). Many wall liner tanks have special corrugations ie 'windows or holes' that bind the walls together at several points. If a wall liner tank is bulging when full of water then you are seeing the effects of the stress the water is placing on the tank. If it stretches too far it can literally burst at the seams. A big flat area in a wall liner is actually a weak area hence the windows or holes in most wall liners and slim line water tanks.
· C/. An underground tank would be heavier yet again. Underground tanks have to take a compression tension - water & soil pressing in on the tank, with different requirements to above ground tanks.
7. Most polyethylene tanks can be installed by DYI'ers without a skilled tradesperson unless hooking up to plumbing in a house or mains water.
8. Guarantee & warranty is not a good indicator on its own. What good is a long warranty on a piece of paper if the tank company has closed down before your tank leaks. It is also very inconvenient to replace the tank.
· 1/. You have to prove the age of the tank or when you purchased it and maybe through whom. Where's your receipt after all these years?
· 2/. The tank manufacturer only has to supply another tank, though they may take the leaking tank away. You are responsible for any new installation costs and pipe work.
· 3/. What about any possible damage that the leaking tank may cause your garden, house or whatever.
Doesn't it make sense to ensure you get a top quality tank in the first place? Don't just take the agent's word for it. Ask questions. At the very least give the tanks a hit test & compare the strengths for yourself. Take a good look at it. If it is already buckled, it will likely stretch even further when full. If the top sags then it is possibly not a strong tank and will sag even more when it is full. Don't forget the straps. If there are straps and bands and braces around or down the sides then that's telling you the plastic is not strong enough without assistance. Run away from these tanks. Spend your hard earned dollars on a good quality tank. You are worth it.
For more information on rainwater tanks see [http://www.coastlineplastics.com.au]
2. Polyethylene is recommended for contact with food & water. It does not leach chemicals into your water. Fibreglass can break down & colorbond steel can rust. Bags & liners can be pierced.
3. Polyethylene is more flexible, relatively lightweight & portable.
4. It is recyclable; though only buy tanks made with virgin plastic. If it has 2 colours or layers then the outside is most likely not virgin plastic and is considerably weaker in structure and is not recommended for contact with food & water.
5. What is the safety factor of the tank you are interested in? The higher the number the stronger the tank. 1 is when the tank is only just strong enough to hold the water when full without bursting. Many only make their tanks to 1.5 times the safety factor. Coastline Plastics are quality manufacturers & their tanks have a minimum standard of 3.5 safety factor. (Which is why they have never had to replace a tank in over 33 years of making tanks) If it has straps around it then it is not strong enough in the original design. (plus the straps are usually made of steel & will rust in time, even stainless steel.)
6. The weight of the tank is an indicator but only in comparisons of tanks of similar size and design. Consider a couple of examples:
· A/. A corrugated look poly tank maybe the same weight but the walls are thinner, because there is more surface area to cover than a in straight wall tank of the same size. Corrugations (like a steel roof) work to make a flat sheet stronger but not in a round tank. (Plus it is an old fashioned look in my opinion).
· B/. A wall liner (or slim line) tank should be heavier than a round tank of the same capacity. (Round tanks are naturally stronger than straight wall tanks as water wants to push out and the pressure is evenly distributed). Many wall liner tanks have special corrugations ie 'windows or holes' that bind the walls together at several points. If a wall liner tank is bulging when full of water then you are seeing the effects of the stress the water is placing on the tank. If it stretches too far it can literally burst at the seams. A big flat area in a wall liner is actually a weak area hence the windows or holes in most wall liners and slim line water tanks.
· C/. An underground tank would be heavier yet again. Underground tanks have to take a compression tension - water & soil pressing in on the tank, with different requirements to above ground tanks.
7. Most polyethylene tanks can be installed by DYI'ers without a skilled tradesperson unless hooking up to plumbing in a house or mains water.
8. Guarantee & warranty is not a good indicator on its own. What good is a long warranty on a piece of paper if the tank company has closed down before your tank leaks. It is also very inconvenient to replace the tank.
· 1/. You have to prove the age of the tank or when you purchased it and maybe through whom. Where's your receipt after all these years?
· 2/. The tank manufacturer only has to supply another tank, though they may take the leaking tank away. You are responsible for any new installation costs and pipe work.
· 3/. What about any possible damage that the leaking tank may cause your garden, house or whatever.
Doesn't it make sense to ensure you get a top quality tank in the first place? Don't just take the agent's word for it. Ask questions. At the very least give the tanks a hit test & compare the strengths for yourself. Take a good look at it. If it is already buckled, it will likely stretch even further when full. If the top sags then it is possibly not a strong tank and will sag even more when it is full. Don't forget the straps. If there are straps and bands and braces around or down the sides then that's telling you the plastic is not strong enough without assistance. Run away from these tanks. Spend your hard earned dollars on a good quality tank. You are worth it.
For more information on rainwater tanks see [http://www.coastlineplastics.com.au]
