Haryana BSEH Senior Secondary NSQF Plumbing flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Confined space oxygen range

Safe entry oxygen level is 19.5% to 23.5% by volume. Below 19.5% is oxygen deficient and above 23.5% is an fire risk; test before entry and ventilate.

H2S in manholes

Hydrogen sulphide is heavier than air, deadens the sense of smell above about 100 ppm, and is the main cause of death in sewer manholes. Never rely on smell.

Pipe wrench jaw rule

Turn a pipe wrench so the force pushes toward the fixed jaw. Reversing the wrench damages the teeth and the pipe, and the joint slips under load.

Gate valve versus globe valve

A gate valve gives full-bore on/off isolation with low head loss. A globe valve gives fine throttling control but causes a high pressure drop across the seat.

BSP taper ratio

Standard pipe thread in India is BSP taper with a 1:16 taper on diameter. A correct joint leaves three to four threads exposed beyond a hand-tight fitting.

Solvent cement cure time

After solvent cementing a UPVC joint, allow 24 hours of cure before pressure testing. Push with a quarter turn and hold for 30 seconds immediately after assembly.

Head to pressure conversion

Each metre of vertical head gives about 9.81 kPa, roughly 1 kg/cm squared. A 10 m head therefore gives about 98 kPa at the outlet.

Overhead tank head rule

Fit the overhead tank at least 2 m above the highest fixture outlet. Below this, gravity flow is poor and a booster pump is needed.

Trap water seal depth

Provide a minimum 50 mm water seal for basins, sinks, and floor traps. Use 75 to 100 mm for WC pans and traps exposed to induced siphonage.

Basin and sink heights

Fix the wash basin rim 750 to 800 mm above finished floor. Fix the sink top 800 to 850 mm and the WC seat 400 to 450 mm above floor.

Drain gradient rule

Lay a 100 mm soil line at 1:40 to 1:60 and a 150 mm line at 1:80 to 1:100. A 50 mm waste runs at 1:30 to 1:40 for self-cleansing flow.

Vent stack size rule

A vent stack must be at least half the soil stack diameter and never smaller than 32 mm. A 100 mm soil stack therefore needs a 50 mm vent.

Drawing scale convention

Use 1:50 for plans and sections, 1:100 for general plans, and 1:20 or 1:10 for details. Always state the scale on the drawing sheet.

Wastage allowance in take-off

Add about 5% to pipe length for cutting waste and 2 to 3% for fittings and offsets when preparing a material take-off from drawings.

Hydrostatic test pressure

Test water supply lines at 1.5 times the working pressure, with a minimum of 0.7 MPa, held for at least one hour with no drop on the gauge.

Drainage air test

Plug the low end and fill the drain with air to 38 to 50 mm water gauge, about 375 to 500 Pa. Hold for 15 minutes with no loss.

Estimate versus quotation

An estimate is an approximate cost given before work starts. A quotation is a firm offer to do the work at a stated price for a stated period.

Break-even point formula

Break-even volume equals fixed costs divided by selling price per unit minus variable cost per unit. Below this volume the enterprise makes a loss.

Fixture unit values

Typical fixture units: WC 6, wash basin 1, sink 2, bath 2, floor trap 1. Sum the values to size the branch and the stack.

Vent termination height

Terminate the vent pipe at least 150 mm above the roof and not within 3 m of an opening window, air intake, or balcony.

Pump total head

Total head equals static lift plus friction loss plus residual pressure needed at the fixture. Select the pump for this head at the required flow rate.

Distribution velocity limit

Keep cold-water velocity in the service line between 0.9 and 1.8 m per second. Above 2 m per second causes noise and pipe erosion.

Cistern float setting

Set the float valve so the shut-off water level is 25 to 40 mm below the overflow pipe. A dual-flush cistern uses 6 litres full and 3 litres reduced.

Geyser relief valve rule

Fit a pressure-relief valve and a non-return valve on a geyser. Never cap or block the relief valve outlet, because the tank can explode.

Fitting take-out

Fitting take-out is the centre-line length a fitting adds to a pipe run. Subtract it from the measured run to get the actual pipe length.

Contract retention

A contract typically retains 5 to 10% of each bill until completion. The balance is released after the defect-liability period ends.

Tank chlorination dose

Dose a new tank to 50 mg per litre free chlorine, contact for 24 hours, then flush until the residual falls below 0.2 mg per litre.

Dripping tap repair

Replace the worn washer or ceramic cartridge to stop a dripping tap. If the valve seat is worn, re-cut it with a seat reamer before fitting the new washer.

Working capital formula

Working capital equals current assets minus current liabilities. A plumbing business needs it to buy material before the client pays the bill.

Résumé structure

A résumé lists contact details, a short summary, skills with levels, work experience with dates and achievements, certifications, and references.

Ladder angle rule

Set a ladder at a 4:1 angle, meaning one unit out for every four units up. Secure it at the top and keep three points of contact while climbing.

Trench shoring depth

Shore or slope any trench deeper than 1.2 m. Keep spoil at least 0.6 m from the edge and provide a ladder every 7.5 m of trench length.