2nd oil tank or a bigger oil tank

[TryAgain1]

I use am outdoor double bunded kerosene oil tank and, because of oil prices, am looking to either:

1) Enlarge the existing oil tank
2) Get a second oil tank and connect to the outlet of the first

Are there any restrictions for 2) e.g. copper pipe diameter upped to 15mm from 10mm due to distance from boiler? Are there any additional valves (e.g. check valve to ensure no backflow from the 1st tank to 2nd tank, e.g. manifold)?

Distance from the 1st oil tank to boiler is about 5m

Advice needed please

 

[Ollyfp]

We secured a grant for an ASHP and solar PV. Our house is well insulated, so this new setup works really well for us. The total cost of heating and hot water is circa £1200 per annum, which is much less than the combined cost of electricity and kerosene.
A friend of mine added a second oil tank (my old one) successfully, so it can be done. Sorry I can't be of more help!