Are all plastic, domestic oil tanks bunded?

[Rollerball]

As I've spent a number of hours over the past couple of days digging out a load of soil from around the lower portion of my plastic oil tank my curiosity about their construction has been aroused.

My plastic tank must be around 20 years old and, in terms of general appearance, looks like the one on the left:

https://b451c108ef7ce3b912eb-75c769...rackcdn.com/cpsfuels/uploads/blog/9_126_l.jpg

at least that is the closest approximation that I can find. It's not exactly the same. Mine also has eight 'feet'. There are also similar inverted 'feet-like' protuberances on top (no doubt to add to the strength). I'd take a photo if my camera was working.

I see from another thread that the main 'feet' apparently also contain oil, this surprised me. Or is that just a secondary containment in case the main cylinder is compromised?

To get back to the question in the title, is my tank likely to be bunded?

Is the main visible plastic simply a strong external shell which surrounds an inner shell which holds the oil? Or, despite appearances, has the design changed much in the past 20 years?

 

[KenGMac]

Rollerball, good evening.

Simple answer is No. Historically these things are not "Bunded"

They are "Double Skinned" [Tank within a tank]

Suggest you consider, erecting some sort of barrier around the tanks to stop direct impact by a vehicle, if indeed vehicles have access to the area where the tanks are placed, Why, Because kerosene is very, very, very difficult to remove once spilled, it will seep into the soil so only remedy is the excavate and remove as "contaminated waste" and if it gets into the house solum then that is a true nightmare to remove?

Ken.

 

[Rollerball]

Thanks for the info and advice.

How much of a gap is there between the two 'layers' of a tank?

Also, here is a tank image which I've just found which looks even more like mine (from one side at least):

https://i.ebayimg.com/images/g/3KMAAOSw-45eMvnz/s-l1600.jpg

With that design is the oil stored solely in the cylindrical part (presumably there's another cylinder inside?) or does that also hold oil in the 'feet'?

On thinking about this though, I once fitted a Watchman Alarm to the tank (like this: https://www.fueltankshop.co.uk/watchman-alarm/p1577 ) and had to use a special hole drilling attachment to make a hole in the top of the tank to fit the Watchman. There was only one thickness of plastic at the top - is it the case that the 'double skin' only applies to the sides and bottom?


Thankfully my tank is in a location where it would be nigh on impossible for a vehicle to hit it.

 

[muggles]

Double skin is all the way round. It's a track within a tank. You can tell whether you have a bunded tank or not by taking the lid off and looking inside. If you see oil, you have a single skin. If you see a second tank and lid, you have a bunded tank.

If your tank is over 20 years old it's almost certainly due for replacement

 

[Rollerball]

Thanks.

Do plastic oil tanks not last much longer than 20 years? Mine is in a shaded area and rarely gets the sun on it, therefore less chance of UV damage for example.

 

[muggles]

It varies according to conditions of course, but single skin ones are more vulnerable. Most s/s tanks only carry a 1 or 2 year warranty from new, bunded ones are usually 10 years. Your OFTEC engineer should produce a TI133D tank condition report as part of your annual boiler service

 

[Rollerball]

I see, thanks. I'll be contacting my OFTEC engineer tomorrow to ask him to make a physical inspection of the tank. There's no problems with it that I'm aware of and I've had a really good look as I've recently been digging some soil away from it.