Oil tank piping Q&A for duplex or dual oil storage tanks.

This article series describes the typical piping arrangements for heating oil storage tanks including how the oil tank fill, vent, and supply piping are arranged when two oil storage tanks (or more) are installed at a building.

FAQs about Piping Hookups for Dual Heating Oil Tanks

These questions & answers about piping connections for dual oil tanks were posted originally at DUAL OIL TANKS - PIPING - please be sure to see the guidelines given there.

Photo at page top: residential dual oil tank installation. Photo just above: a pair of oil tanks outside a commercial facility in New Zealand, photographed by the author [DF].

[Click to enlarge any image]

Question: how to get oil out of the second oil tank

(Aug 8, 2012) Help! said:
Have a dual oil tank system that was improperly installed (I have been told). There is a feed to oil burner only in 1 tank, but oil in both tanks. Can a feed be installed in the second tank, even though there is oil in it?

Reply:

Help:

Well you could take an oil line feed off of the top of a tank filled with oul, but I think it would be a horrible mess to try to connect oil piping to the bottom of an oil tank that was full.

Question:

(Feb 27, 2014) John said:
This system is a poor configuration. The tank with least backpressure fills first them forces oil into the vent piping and is the forced out by air leaving the not full tank. This results in a full tank and a not full tank and sometimes a oil blowout from the vent pipe.

Reply:

Thanks John, thats interesting. Since we're showing common oil fill and vent piping arrangements, what do you recommend and what sources can you suggest so that we can update or expand this information. I have not found an expert source that makes the same claim as your note.

At buildings where two heating oil storage tanks are installed, typically indoors, this Audel Oil Burner Guide sketch shows the proper arrangement of fill piping, vent piping, and oil line piping leaving the tanks.

On 2019-02-17 by (mod) -

Thanks for the interesting opinion, David. We want to be careful to distinguish between what we think and what's authoritative or what's required by building codes and standards.

Your idea is one worth keeping in mind; still I'd argue (thus my OPINION not fact) that most heating oil leaks occur from either leaks in the steel tank body or leaks at poorly-made piping connections.

As Carson Dunlop Associates ' sketch (left) demonstrates,it was common to run oil piping under a residential floor slab; the installers may have opined that protecting the oil line from damage was solving a greater problem than a corrosion-leak risk.

Worth noting:

• Sandberg, Chet, Jim Holmes, Ken McCoy, and Heinrich Koppitsch. "The application of a continuous leak detection system to pipelines and associated equipment." In Record of Conference Papers., Industrial Applications Society 35th Annual Petroleum and Chemical Industry Conference,, pp. 241-244. IEEE, 1988.
• Berg, Jost. "Leak detection device for double-wall pipeline systems and container systems." U.S. Patent 6,489,894, issued December 3, 2002.

Interestingly none of the patents I could find cited any actual statistics on where oil leaks occur. However we have researched that topic.

While small residential oil storage tank and piping leaks do occur as drips or seeps at oil piping connections, those generally lead quickly to such poor oil burner operation (due to air leaking into the piping system and terrible oil burner operation, ultimately loss of heat) that they get discovered and fixed in most cases.

See OIL TANK LEAKS & SMELLS - home - to find our research results.

The more-costly oil storage system leaks occur from corrosion - water inside oil storage tanks - of which buried tanks are usually the most-costly to discover and correct.

On 2019-02-17 by David

Worth mentioning, the 2009 picture at DUAL OIL TANKS - PIPING shows the oil feed being run under the concrete floor. Home inspectors will have a problem with this especially during a purchase/sale of a home, because oil leaks are not visible and could lead to groundwater contamination.

A better option would be to encase the oil feed in a separate pipe on top of the concrete.

On 2018-02-01 by (mod) -

Check first for a stuck fuel gauge

On 2018-02-01 by Anthony

I have 2 tanks and usually upon fuel delivery the tanks would always equal. But now it seems only the one tank is full and the other is empty. I am afraid that the empty one is the one that feeds my burner.

On 2018-01-31 by (mod) -

Anonymous

Thank you for your helpful comments for Peter. If you want to be identified and linked-to as a technical contributor just use the page top or bottom CONTACT link to send me a note.

Daniel

On 2018-01-31 by Anonymous

@Peter,
They should draw evenly. Make sure the 2 tanks are the same height. A furnace fuel draw is measured by height not distance. Most can lift fuel about 8-10 feet so having fuel across the basement isn't a problem. It probably only lifts the fuels a foot or two max.

On 2018-01-31 by Anonymous

@Anonymous,
Either the fuel supply line is plugged between the 2 tanks or it is turned off and you're only using one tank.

On 2018-01-31 by Anonymous

@Cyntjia,
The fuel supply line to your furnace makes the 2 tanks equal and use equally so one gauge will show one tank but both tanks should be at that level

On 2018-01-31 by Peter

Your picture shows a good hook-up. The diagram shows the fill and vent pipes going through a T and connecting to each tank.

The only way that works with out have oil spill out the vent is if you have a 2" pipe across the bottom of the tanks to make sure they are filled evenly. When fuel is flowing it will always put more in one tank and not split 50-50 through the T connecting the 2 tanks together.
I've been delivering fuel for 10+ yrs.

And have never had the T connection work without the bottom of the tanks connected together with the same size pipe as the fill.

On 2018-01-16 by (mod) -

Cyn
Usually common piping between the two tanks keeps their oil level at the same point in both tanks.

Therefore a guage on one tank is reading the common oil level in both tanks.

On 2018-01-16 by Cyntjia

How does one oil level work on dual tanks.

On 2017-11-10 by Anonymous

I have 2 indoor oil tanks. As of recently only one tank is filling with delivery. The driver stated the whistle said they were full but only one tank is full? What would cause this to happen?

On 2017-06-17 20:13:21.072692 by Peter

I have one 275 gallon tank in my basement and would like to add another 275 gallon. The second tank would be about 18 feet from each other.

Can I run a fuel line from one and connect to the other fuel line and then run one fuel line to the burner so that I would be drawing off both tanks at same time. Or would that be too far or not draw even from both.
Thanks Peter

...

Continue reading at DUAL OIL TANKS - PIPING - topic home, or select a topic from the closely-related articles below, or see the complete ARTICLE INDEX.

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DUAL OIL TANKS - PIPING FAQs at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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INDEX to RELATED ARTICLES: ARTICLE INDEX to HEATING OIL, OIL BURNERS, OIL FIRED HEATERS, OIL TANKS

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