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Discussion Starter #1
I have two 275 oil tanks that are connected via a T in the lines going to the furnace. One is on its side (horizontal 275) and one is standing up. The horizontal one has over flowed before. When filling up I thought they were connected in the sense that they would self level and even out but the oil company filled 1 (275H) and the other one (275V) is still at 1/4 full.
My question is this...
Will they eventually even out?
Is there any danger of the horizontal tank overflowing if the vertical is filled second or did the oil company just make a mistake that one time?
And finally, can I run it as is or is there a danger in completely emptying an oil tank?
I wasn't sure if there was debris or odd things that happen when an oil tank is sucked completely dry.
Thank you for your help and advice!
 

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If there is an opening in the lower tank below the fill level of the other tank it could overflow as the oil balances its level between the two tanks. If all the fills and overflows are at the same level there should be no overflowing unless there is a leak.
 

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If there is an opening in the lower tank below the fill level of the other tank it could overflow as the oil balances its level between the two tanks. If all the fills and overflows are at the same level there should be no overflowing unless there is a leak.
So if the connection between the tanks is lower than both tanks, they may still level out?
 

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Unless there are check valves in the lines then oil between the tanks will level out. A check valve would allow oil to flow out but not back in.
You would need the oil to level out otherwise one tank could run dry and furnace would suck air from that tank unless you have manual control valves to switch between tanks.
 

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Discussion Starter #7
Unless there are check valves in the lines then oil between the tanks will level out. A check valve would allow oil to flow out but not back in.
You would need the oil to level out otherwise one tank could run dry and furnace would suck air from that tank unless you have manual control valves to switch between tanks.
So definitely do not run it with one empty and the other full? That's good to know cause that's exactly what I was planning on doing.
If they don't level out, then I'll get the one filled.
 

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Are these definitely connected together?
I’ve never seen connected tanks differing in layout, and so far apart. What’s the piping look like?
 

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I would suspect that the T connection under the oil tanks is partly clogged so oil does not equalize between the tanks easily.

I would expect that with a T connection at least 3/4 inch inside diameter and below the levels of both tank bottoms and also no check valves you would not have a problem of one tank emptying out first and then the oil burner sucking air. Each tank should have its own full indicator whistle.

But when the delivery guy comes and starts to fill one tank, the T connection will not equalize fast enough to fill both tanks from one fill point before the whistle indicates full. And it will not be possible to guess when to move the nozzle to the other tank's fill point because additional equalizing will occur while he moves the nozzle.So long ast the pipework is properly sealed (pipe dope, Teflon tape or whatever) and the two fill points are above the tops of both tanks, you should not get an overflow from the second tank before the first is full.
 

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So definitely do not run it with one empty and the other full? That's good to know cause that's exactly what I was planning on doing.
If they don't level out, then I'll get the one filled.
It should not be possible to run one tank empty if they are piped together. It's all speculation unless we know exactly what you have.
 

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That small copper pipe isn’t sufficient to be used to equalize the tanks. Should be something of a larger diameter.
Does it run along the floor the whole way between the tanks?
It’s likely clogged.
Those tanks shouldn’t have been connected together like that, being that far apart.
 

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It might not be big enough to equalize on filling but it will cause the tanks to equalize over time unless it is clogged.
 

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Discussion Starter #18
It might not be big enough to equalize on filling but it will cause the tanks to equalize over time unless it is clogged.
The horizontal tank does get drained during regular use so I don't think its clogged. I'll keep an eye on the vertical tank. From what u all have said I should definitely not run the vertical tank dry so if that drops then I'll have to order another delivery.
 
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