307A hydronic, process and gas piping practice questions.

Five free practice questions on hydronic, process and gas piping: block E of the Red Seal 307A Steamfitter/Pipefitter exam, about 27 of its 130 questions. They are in the exam's format: four options, one correct answer. Answer each one before opening the explanation. No account, no email.

01The questions

1. Procedural · Installs piping for hydronic systems

   In a school retrofit, new radiant-floor PEX loops will be served from an existing 180 °F (82 °C) boiler loop with a cast-iron boiler. The floor's design supply is 110 °F (43 °C). Which approach is correct?

   1. Non-barrier PEX fed straight from the boiler loop, zone valve throttled
   2. Non-barrier PEX with a mixing valve and a bronze circulator
   3. Oxygen-barrier PEX fed straight from the boiler loop at 180 °F
   4. Oxygen-barrier PEX, fed through a mixing device that lowers the supply
   Show the answer

   D. Correct. A mixing device (3-way or 4-way mixing valve or injection pumping) blends return water into the supply so the floor sees its 110 °F design temperature, protecting the slab, flooring and tubing. Oxygen-barrier PEX stops oxygen diffusing through the tube wall into a system with iron components.

   Why not the others

   A. Throttling a zone valve reduces flow, not supply temperature, so the first part of the floor still sees 180 °F. Non-barrier PEX also lets oxygen diffuse into the water and corrode the cast-iron boiler and steel components.

   B. Mixing is right, but non-barrier PEX lets oxygen into the whole system, not just the pump; the cast-iron boiler and steel piping would still corrode. Use barrier PEX or separate the floor with a heat exchanger.

   C. The barrier tubing is right, but 180 °F into a slab overheats the floor surface and coverings and exceeds the design. The supply temperature must be reduced by mixing or injection.

2. Procedural · Installs piping for process piping systems

   A Type L copper cooling-water line in a pulp mill must connect to a carbon-steel header. What is installed at the connection?

   1. A galvanized steel coupling between them
   2. A dielectric union or insulating flange kit
   3. Extra PTFE tape on the threaded joint
   4. A copper adapter threaded straight into the steel
   Show the answer

   B. Correct. Copper and carbon steel in contact in water form a galvanic cell, and the steel, the less noble metal, corrodes at the joint. A dielectric union or an insulating flange kit (gasket, sleeves and washers) breaks the electrical path between them.

   Why not the others

   A. Galvanized steel is still less noble than copper; the zinc corrodes first and then the steel. It adds another metal to the cell rather than isolating the two.

   C. PTFE tape seals threads but does not reliably insulate them; thread contact still conducts, and the water completes the galvanic cell. Use a dielectric union or insulating flange kit.

   D. Threading a copper adapter directly into steel puts the dissimilar metals in electrical contact in the water, so the steel threads corrode away. An insulating fitting is needed.

3. Procedural · Installs piping for industrial water and waste treatment systems

   A 12-inch ductile-iron pressure line with push-on joints feeds a water treatment plant and turns 90° underground. What must be provided at the bend?

   1. Thrust restraint: a thrust block or restrained joints
   2. An expansion joint to absorb pipe growth
   3. A flexible coupling to allow joint deflection
   4. Nothing extra; the gaskets hold the fitting
   Show the answer

   A. Correct. Internal pressure pushes on a bend (and on tees, dead ends and reducers) with a large unbalanced force. Push-on and mechanical joints have little resistance to pulling apart, so the fitting is held by a concrete thrust block against undisturbed soil or by restrained joints over the calculated length, in place before the pressure test.

   Why not the others

   B. A buried water line sees little temperature change, and an expansion joint adds another place for the fitting to push apart. The concern at a bend is hydraulic thrust.

   C. Flexibility makes the problem worse: the thrust at the bend would push the joint apart. The joint must be restrained or the fitting blocked.

   D. Rubber gaskets seal but do not resist pull-out. Without restraint the thrust at the bend separates the joint, often during the pressure test.

4. Procedural · Installs piping for compressed air and pneumatic systems

   A branch is being taken off a horizontal compressed-air main to feed a machine in a sawmill. Where on the main should the branch connect?

   1. The bottom of the main, dropping straight down
   2. The side of the main, horizontally
   3. The end of the main, past the last drain
   4. The top of the main, looping up and over
   Show the answer

   D. Correct. Water and oil condensed in the main run along its bottom toward the drain legs. A branch taken off the top (a swan neck or gooseneck) draws drier air and leaves the liquid in the main; the drop then runs down to the machine and ends in a drain leg with the outlet above it.

   Why not the others

   A. A bottom connection drains the main's condensate straight into the branch and the machine. Branches come off the top.

   B. A side connection still picks up condensate running along the pipe, especially at high flow. The top take-off is standard.

   C. The end of a main collects condensate and is where a drain leg belongs. Branches are taken from the top along the main.

5. Recall · Installs piping and hoses for hydraulic systems

   A steamfitter is flaring steel tube for a hydraulic line with JIC fittings. Which flare angle is used, and what is the rule about mixing?

   1. 37°, interchangeable with 45° SAE fittings
   2. 37°, never mated with 45° SAE fittings
   3. 45°, the same as refrigeration flares
   4. 45°, interchangeable with 37° JIC fittings
   Show the answer

   B. Correct. JIC hydraulic fittings use a 37° flare; SAE refrigeration and gas flare fittings use 45°. They can look alike and even thread together in some sizes, but the seats do not match, so the joint seals only on a line and fails under hydraulic pressure. Never mix them.

   Why not the others

   A. 37° is right for JIC, but the two angles are never interchangeable; the mismatched seats touch only on a line and fail.

   C. 45° SAE flares are the refrigeration and gas standard. Hydraulic JIC fittings use 37°, and the two must not be mixed.

   D. 45° is the SAE flare used for refrigeration and gas. Mixing it with 37° JIC seats leaves a line contact that leaks or blows apart under pressure.

02Answer key

03What block E covers

This block covers the heating, cooling and process systems a steamfitter installs and services. It includes hydronic heating and chilled water, expansion tanks and air removal, process piping and pump connections, water treatment, hydraulic circuits, HVACR piping, natural gas, propane and fuel oil, medical gas, compressed air and fire protection systems.

The Red Seal Occupational Standard names this block “Installs, tests, maintains, troubleshoots and repairs heating, cooling and process piping systems”. It carries 20.8% of the exam, about 27 of the 130 questions, split across nine tasks. The share column is each task's weight within the block, as the standard publishes it.

04What the questions turn on

Pumping away from the tank

Connect the expansion tank at the pump suction with the pump pumping away, so the pump's head shows up as a pressure rise in the system. Set the tank's air pre-charge to the static fill pressure while the water side is empty.

Fill pressure from building height

Divide the height to the top radiation by 2.31 ft per psi, then add about 4 psi to keep the high point positive. Fill pressure set too low leaves top-floor units cold and gurgling while the lower floors heat normally.

Flow from the load

Water flow in US gpm is the load in Btuh divided by 500 times the temperature difference. One ton of cooling is 12 000 Btuh, which works out to about 2.4 gpm per ton at a 10 °F difference.

Brazing and testing medical gas

Copper-to-copper medical gas joints are brazed with BCuP-3 or BCuP-5 and no flux, with oil-free dry nitrogen flowing while the joint is hot. The cross-connection test pressurizes one system at a time and checks that only its outlets flow.

05The other blocks

The 307A exam has seven blocks. Each has its own page of free questions:

The 307A Steamfitter/Pipefitter practice exam page describes the full question bank. How these questions are written and checked: how our questions are made. Found a mistake? Tell us and we will fix it.