Oil Storage and Piping Systems

Introduction to Fuel Oil Storage

Fuel oil storage and piping form the backbone of any oil heating system. As an oil heating system technician, you must have a thorough command of the design, installation, and maintenance rules for tanks and piping, since a failure in this area can lead to leaks, fires, or serious environmental damage. This chapter covers all the knowledge required for the Red Seal exam, focusing on Canadian national standards, essential calculations, and compliant installation procedures.

Types of Storage Tanks

Above-Ground Storage Tanks

Above-ground tanks are the most common in residential and light commercial installations. They are manufactured from steel or reinforced fibreglass (RFG). Steel is the traditional material, offering excellent mechanical strength, but it is susceptible to internal and external corrosion. RFG tanks are becoming increasingly popular due to their corrosion resistance, but they require special precautions during installation (continuous support, UV protection).

Standard Capacities: Residential tanks typically range from 227 L (50 imperial gallons) to 1,000 L (220 imperial gallons). Commercial tanks can reach 5,000 L or more.

Underground Storage Tanks (UST)

Underground tanks are used when space is limited or for aesthetic reasons. They must be double-wall steel or double-wall RFG to meet environmental requirements. The installation of underground tanks is strictly regulated by provincial and federal authorities. The Canadian Electrical Code, Part I (CE Code) applies to associated electrical equipment, while CSA B139 (Installation Code for Oil-Burning Equipment) governs the complete installation.

Double-Wall Tanks

Double-wall tanks offer additional protection against leaks. The interstitial space (between the two walls) can be equipped with a leak detector or a monitoring system. This configuration is mandatory for underground tanks in most Canadian jurisdictions.

Installation Rules for Above-Ground Tanks

Location and Clearances

According to CSA B139, above-ground tanks must respect minimum clearances from buildings and property lines:

Tank Type	Minimum Clearance from Building	Minimum Clearance from Property Line
Tank ≤ 2,500 L	1.5 m (5 ft)	1.5 m (5 ft)
Tank > 2,500 L	3 m (10 ft)	3 m (10 ft)
Underground tank	1 m (3 ft)	1 m (3 ft)

Exception: A tank with a capacity of ≤ 2,500 L may be installed less than 1.5 m from a building if the building wall is made of non-combustible material and no openings (doors, windows) are located within 1.5 m of the tank.

Support and Leveling

Above-ground tanks must be installed on a stable, level base capable of supporting the total weight of the filled tank. The weight of oil is approximately 0.85 kg/L (7.1 lb/imperial gallon). For a 1,000 L tank, the total oil weight is 850 kg, plus the weight of the tank itself (approximately 150 kg), for a total of about 1,000 kg.

Total Weight Calculation:

Total weight = (Capacity in L × 0.85 kg/L) + Weight of empty tank

Example: 1,000 L tank (empty weight = 150 kg)

Total weight = (1,000 × 0.85) + 150 = 1,000 kg

The base must be concrete (minimum 100 mm thick) or compacted gravel, with a flat surface. Tanks must be installed with a slight slope (approximately 2%) toward the drain point or purge valve.

Tank Venting

Each tank must be equipped with a vent sized according to the tank capacity and filling rate. The vent must:

Have a minimum diameter of 50 mm (2 in) for tanks ≤ 2,500 L

Be located at least 1.2 m above ground level

Be oriented downward to prevent rainwater entry

Be equipped with a screen to prevent insect entry

Important Rule: The vent must be sized to allow air to escape during filling. A blocked vent can cause positive pressure in the tank, leading to tank deformation or explosion.

Oil Piping: Fundamental Principles

Piping Materials

Oil lines must be made of copper (Type L or K) or black steel (Schedule 40). Copper is the most common material for residential installations due to its ease of installation and corrosion resistance. Steel is used for commercial installations or where lines are exposed to mechanical damage.

Material	Maximum Diameter	Typical Use
Copper Type L	25 mm (1 in)	Residential
Copper Type K	25 mm (1 in)	Underground
Black steel sch. 40	All diameters	Commercial, exposed

Prohibition: Copper Type M is prohibited for oil lines due to its thinner wall and lower corrosion resistance.

Pipe Sizing

The pipe diameter depends on the equivalent length of the circuit (actual length + fitting friction losses) and the flow rate required by the burner. The flow rate is determined by the burner capacity in gph (gallons per hour) or L/h.

Conversion Formula:

1 gph = 3.785 L/h

Required Flow Rate:

Flow rate (L/h) = Burner rating (kW) ÷ (Heating value of oil × Efficiency)

The heating value of No. 2 fuel oil is approximately 38.2 MJ/L (10.6 kWh/L). With an efficiency of 80%, a 25 kW burner requires:

Flow rate = 25 ÷ (10.6 × 0.80) = 2.95 L/h

Recommended Sizing Table (Copper)

Total Equivalent Length	Maximum Flow Rate (L/h)	Tube Outside Diameter
≤ 15 m	4 L/h	6.35 mm (1/4 in)
≤ 30 m	8 L/h	9.52 mm (3/8 in)
≤ 60 m	15 L/h	12.7 mm (1/2 in)
≤ 100 m	25 L/h	15.88 mm (5/8 in)

Rule of Thumb: For most residential installations (distance < 15 m), a 6.35 mm (1/4 in) tube is sufficient for a standard 0.75 to 1.00 gph burner. For longer installations or higher-capacity burners, use the table above.

Oil Supply Systems

Gravity System

The gravity system uses the height of the oil column to feed the burner. The tank must be located above the burner level. The minimum height is 1 m (3 ft) between the oil level and the burner. This system is simple and reliable, but it is limited to installations where the tank is elevated.

Advantages: Simplicity, no pump, reliability.

Disadvantages: Requires an elevated tank, risk of gravity flow leak in case of line rupture.

Barometric Loop System

The barometric loop system uses a line that rises above the oil level of the tank before descending back down to the burner. This configuration creates a siphon that prevents oil from flowing by gravity in the event of a leak. The height of the loop must be at least 1 m above the maximum oil level.

Application: Used when the tank is located at a level higher than the burner, but you want to prevent gravity flow in case of a leak.

Pump System (Two-Pipe System)

The two-pipe system (supply and return) is the most common for modern installations. A pump (usually integrated into the burner) draws oil from the tank and delivers it to the burner. Excess oil returns to the tank through the return line.

Advantages: Allows the tank to be installed at a level lower than the burner, automatic air purging, constant flow rate.

Maximum Lift: The standard pump can lift oil up to 3 m (10 ft) of vertical height and 6 m (20 ft) of horizontal length. Beyond that, a two-stage pump or an auxiliary pump is required.

Equivalent Length Calculation

The equivalent length (EL) accounts for friction losses in fittings. Each fitting adds a fictitious length of pipe:

Fittings	Equivalent Length (m) for 6.35 mm tube
90° elbow	0.6 m
45° elbow	0.3 m
Tee (straight through)	0.3 m
Tee (branch)	1.2 m
Shut-off valve	0.3 m
Filter	1.5 m

Formula:

Total EL = Actual length + Σ (Equivalent lengths of fittings)

Example: A 10 m line with 4 – 90° elbows, 1 valve, and 1 filter.

EL = 10 + (4 × 0.6) + 0.3 + 1.5 = 10 + 2.4 + 0.3 + 1.5 = 14.2 m

Piping Components

Oil Filters

Each installation must include an oil filter between the tank and the burner. The filter must be installed:

As close as possible to the tank

With a pressure gauge or clogging indicator if possible

With a transparent bowl for visual inspection (for cartridge filters)

Filter Screens: Screen filters have a mesh of 100 to 150 microns. Cartridge filters provide filtration of 10 to 30 microns.

Rule: The filter must be replaced at least once a year, or more frequently if the oil is contaminated.

Shut-Off Valves

A shut-off valve must be installed:

At the tank outlet (main valve)

At the burner inlet (isolation valve)

On each return line (if applicable)

Valves must be ball valves or needle valves for small-diameter lines. Gate valves are prohibited for oil due to their tendency to leak.

Check Valves

A check valve is required on the suction line to prevent oil from returning to the tank when the pump stops. This valve is essential for maintaining pump prime.

Installation: The check valve must be installed at the end of the suction line, inside the tank, or immediately at the tank outlet.

Safety Devices

Leak detector: Mandatory for underground tanks and recommended for above-ground tanks.

Pressure relief valve: Installed on tanks to relieve excessive pressure in case of fire.

Level gauge: Indicates the oil level in the tank. Gauges can be mechanical (float) or electronic.

CSA B139 Rules

General Requirements

CSA B139 (Installation Code for Oil-Burning Equipment) is the national reference standard for installing oil heating systems. Key points include:

Rule 4.3.1: All tanks must be installed in accordance with the manufacturer's specifications and the requirements of the standard.

Rule 4.4.2: Above-ground tanks must be equipped with a level indicator or gauge.

Rule 4.6.1: Oil lines must be supported at maximum intervals of 1.5 m for 6.35 mm tubes and 2 m for larger diameter tubes.

Rule 4.7.1: All oil lines must be leak-tight and tested at a pressure of 100 kPa (15 psi) for at least 15 minutes before commissioning.

Leak Testing

The leak testing procedure is crucial:

96.Fill the system with oil or compressed air

97.Pressurize to 100 kPa (15 psi)

98.Maintain the pressure for 15 minutes

99.Verify there is no pressure drop

100.Visually inspect all connections for leaks

Caution: Never use a flame to detect oil leaks. Use a leak detector solution (soapy water) or an electronic detector.

Corrosion Protection

Steel tanks must be protected against corrosion:

Exterior coating: Epoxy paint or other protective coating

Cathodic protection: Sacrificial anodes (magnesium or zinc) for underground tanks

Isolation: Above-ground tanks must be isolated from the concrete base using wood or plastic supports to prevent corrosion from contact

Pipe Sizing Calculations

Calculation Method

To properly size an oil line, follow these steps:

Step 1: Determine the required burner flow rate (in L/h)

Step 2: Calculate the total equivalent length (EL)

Step 3: Consult the sizing table (see previous section)

Step 4: Verify the maximum lift

Complete Example:

1.00 gph burner → Flow rate = 3.785 L/h

Actual length: 12 m

Fittings: 3 – 90° elbows, 1 valve, 1 filter

EL = 12 + (3 × 0.6) + 0.3 + 1.5 = 15.6 m

Required diameter: 6.35 mm (1/4 in) (maximum flow rate 4 L/h for 15 m)

Lift: 2 m (within the 3 m limit)

Lift Calculation

The maximum lift depends on atmospheric pressure (approximately 101 kPa at sea level) and the density of oil (approximately 850 kg/m³).

Formula:

Maximum height (m) = Atmospheric pressure (Pa) ÷ (Oil density (kg/m³) × g)

Where g = 9.81 m/s²

Calculation:

Maximum height = 101,000 ÷ (850 × 9.81) = 12.1 m

However, in practice, the maximum lift is limited to 3 m for standard pumps due to friction losses in the line and pump operating requirements.

Installation Procedures

Above-Ground Tank Installation

131.Site preparation: Level the ground, pour a concrete slab (100 mm minimum)

132.Tank placement: Install on supports (treated wood or plastic), verify leveling

133.Piping connection: Install the main valve, filter, and lines to the burner

134.Vent installation: Mount the vent with its screen

135.Gauge installation: Install the level gauge

136.Leak test: Pressurize the system to 100 kPa for 15 minutes

137.Filling: Fill the tank and verify burner operation

Underground Tank Installation

139.Excavation: Dig a pit with sufficient depth (minimum 600 mm of cover)

140.Sand bed: Install a bed of sand or fine gravel (150 mm)

141.Tank placement: Lower the tank carefully, verify leveling

142.Connection: Install the lines, vent, and leak detection devices

143.Backfilling: Fill the pit with sand or gravel, compacting in layers

144.Leak test: Perform the test at 100 kPa

145.Documentation: Document the installation for environmental authorities

Preventive Maintenance

Annual Inspection

The annual inspection must include:

Visual inspection of the tank (rust, dents, leaks)

Inspection of the piping (corrosion, supports, leaks)

Replacement of the oil filter

Verification of the level gauge

Burner operation test

Verification of the vent (obstruction)

Leak Detection

Signs of a leak include:

Oil odour in the basement or outside

Oil stains on the floor or walls

Abnormal oil consumption

Dead vegetation around the tank

Procedure in case of a leak:

162.Immediately close the main valve

163.Evacuate the area

164.Contact environmental authorities

165.Do not use electrical equipment nearby

166.Ventilate the area

Summary

Above-ground tanks must respect the minimum clearances of CSA B139 (1.5 m for ≤ 2,500 L)

The weight of oil is 0.85 kg/L; the total weight of the filled tank must be calculated for the base

The vent must have a minimum diameter of 50 mm and be oriented downward

Oil lines are copper Type L or K or black steel; copper Type M is prohibited

The burner flow rate is calculated: Flow rate (L/h) = Power (kW) ÷ (10.6 × Efficiency)

The equivalent length includes fitting friction losses

The maximum lift is 3 m for standard pumps

The leak test is performed at 100 kPa for 15 minutes

A check valve is required on the suction line

The oil filter must be replaced annually

Ball valves or needle valves are required; gate valves are prohibited

Common Pitfalls to Avoid

180.Confusing units: Do not confuse imperial gallons (4.546 L) and US gallons (3.785 L). In Canada, the imperial gallon is used for tanks, but burner flow rates are often expressed in US gph.

181.Forgetting the equivalent length: Many candidates size lines based only on the actual length. Always add the equivalent lengths of fittings.

182.Neglecting the lift: A standard pump cannot lift beyond 3 m. Beyond that, a two-stage pump or an auxiliary pump is required.

183.Using copper Type M: Copper Type M is prohibited for oil. Use only Types L or K.

184.Installing the vent upward: The vent must be oriented downward to prevent water entry. An upward-oriented vent is a common error.

185.Forgetting the check valve: Without a check valve, oil returns to the tank and the pump loses its prime.

186.Testing with a flame: Never use a flame to detect oil leaks. Use a leak detector solution or soapy water.

187.Confusing pressures: The leak test is performed at 100 kPa (15 psi), not 100 psi. Always check the units.

188.Ignoring the slope of lines: Horizontal lines must have a slight slope (1–2%) toward the tank to allow oil to return.

189.Forgetting corrosion protection: Steel tanks must be protected against corrosion, especially at points of contact with soil or concrete.

190.Not checking leveling: A poorly leveled tank can lead to water accumulation and accelerated corrosion.

191.Undersizing the vent: A vent that is too small can cause excessive pressure during filling, deforming the tank.

192.Installing the filter after the pump: The filter must be installed before the pump (suction side) to protect the pump from contaminants.

193.Confusing one-pipe and two-pipe systems: A one-pipe system is used when the tank is above the burner; a two-pipe system is used when the tank is below. Do not confuse them.

194.Forgetting environmental requirements: Underground tanks have additional requirements (leak detection, registration) that must not be neglected.

This chapter covers all the essential knowledge for the Red Seal exam regarding oil storage and piping. Master these concepts, calculations, and CSA B139 rules, and you will be well prepared for exam questions on this topic.

Oil Storage and Piping Systems