mechanical-plumbing-systems

# Mechanical & Plumbing Systems Guide Quick reference for construction project managers and field supervisors managing HVAC (Division 23) and plumbing (Division 22) trades on commercial and institutional projects. ## Quick Reference Tables ### HVAC Equipment Types | Equipment | Typical Application | Key Installation Concerns | Long-Lead Time | |-----------|---------------------|---------------------------|----------------| | Air Handling Unit (AHU) | Large commercial spaces | Rigging access, vibration isolation, coil piping | 12-20 weeks | | Rooftop Unit (RTU) | Single-story retail/office | Roof structure, curb detail, crane access | 8-16 weeks | | Chiller (Air-Cooled) | Medium buildings | Pad/dunnage, electrical, clearances | 16-24 weeks | | Chiller (Water-Cooled) | Large buildings | Rigging, chilled/condenser water piping | 20-30 weeks | | Boiler (Hot Water) | Heating systems | Venting, gas piping, expansion tank | 12-20 weeks | | Cooling Tower | Water-cooled systems | Structural support, water treatment | 14-22 weeks | | VRF/VRV System | Multi-zone buildings | Refrigerant piping lengths, branch boxes | 12-18 weeks | | Fan Coil Unit | Hotels, apartments | Condensate drain, coordination | 8-12 weeks | → See [hvac-equipment.md](references/hvac-equipment.md) for detailed specifications and installation requirements. ### Ductwork Pressure Classes & Sealing | Pressure Class | Static Pressure | Typical Application | Seal Class | |----------------|-----------------|---------------------|------------| | 0.5" WG | ±0.5" | Low-velocity return | C (transverse only) | | 1" WG | ±1" | Low-pressure supply | B (transverse + longitudinal) | | 2" WG | ±2" | Medium-pressure supply | A (all seams + joints) | | 3" WG | ±3" | High-pressure main ducts | A | | 4" WG | ±4" | VAV systems | A | | 6" WG | ±6" | High-velocity systems | A | | 10" WG | ±10" | Industrial/exhaust | A | → See [ductwork-distribution.md](references/ductwork-distribution.md) for SMACNA standards and installation details. ### Pipe Material Selection Guide | System | Common Materials | Joining Method | Max Temp | |--------|------------------|----------------|----------| | Chilled Water | Steel (Sch 40) | Welded, grooved | 200°F | | Hot Water <2" | Copper Type L | Soldered, press-fit | 400°F | | Hot Water >2" | Steel (Sch 40) | Welded, grooved | 200°F | | Steam | Steel (Sch 40/80) | Welded | 366°F (150 psi) | | Refrigerant | ACR Copper | Brazed | Per refrigerant | | Domestic Cold | Copper Type L, CPVC, PEX | Various | 180°F (copper) | | Domestic Hot | Copper Type L, CPVC, PEX | Various | 180°F | | Sanitary Drain | Cast Iron, PVC DWV | Hub, no-hub, solvent | 140°F (PVC) | | Storm Drain | Cast Iron, PVC | Hub, no-hub, solvent | N/A | → See [piping-systems-hvac.md](references/piping-systems-hvac.md) and [plumbing-piping-water.md](references/plumbing-piping-water.md) for complete specifications. ### Pipe Support Spacing (Horizontal) | Pipe Size | Steel Pipe | Copper Tube | CPVC | PVC/ABS | |-----------|------------|-------------|------|---------| | 1/2" | 7 ft | 5 ft | 3 ft | 4 ft | | 3/4" | 7 ft | 5 ft | 3 ft | 4 ft | | 1" | 7 ft | 6 ft | 3 ft | 4 ft | | 1-1/4" | 7 ft | 7 ft | 4 ft | 4 ft | | 1-1/2" | 9 ft | 8 ft | 4 ft | 4 ft | | 2" | 10 ft | 8 ft | 4 ft | 4 ft | | 2-1/2" | 11 ft | 9 ft | 5 ft | 5 ft | | 3" | 12 ft | 10 ft | 5 ft | 5 ft | | 4" | 14 ft | 12 ft | 6 ft | 5 ft | | 6" | 17 ft | 14 ft | 8 ft | 5 ft | | 8" | 19 ft | 16 ft | N/A | 5 ft | ### DWV Pipe Slope Requirements | Pipe Size | Minimum Slope | Standard Slope | |-----------|---------------|----------------| | Up to 3" | 1/4" per foot | 1/4" per foot | | 4" and larger | 1/8" per foot | 1/8" per foot | | Building drain | 1/8" per foot minimum | 1/4" preferred | → See [plumbing-fixtures-drainage.md](references/plumbing-fixtures-drainage.md) for complete drainage system requirements. ### Insulation Thickness Requirements (ASHRAE 90.1) | System | Pipe Size | Temperature Range | Minimum Thickness | |--------|-----------|-------------------|-------------------| | Chilled Water | <1" | 40-55°F | 1" | | Chilled Water | 1" to 1-1/2" | 40-55°F | 1" | | Chilled Water | 2" to 4" | 40-55°F | 1.5" | | Chilled Water | >4" | 40-55°F | 1.5" | | Hot Water | <1" | 105-140°F | 1" | | Hot Water | 1" to 2" | 105-140°F | 1.5" | | Hot Water | >2" | 105-140°F | 2" | | Steam/Condensate | All | >200°F | 2" minimum | | Refrigerant Suction | All | Below ambient | 3/4" elastomeric | → See [insulation-requirements.md](references/insulation-requirements.md) for complete insulation schedules. ### Required Inspections & Hold Points | Phase | Inspection Required | Key Items to Verify | |-------|---------------------|---------------------| | Underground Rough | Plumbing underground | Slope, bedding, joints, cleanouts | | Slab Prep | Below-slab piping | Water test complete, sleeves placed | | Overhead Rough | Above-ceiling MEP | Hangers, slopes, accessibility | | Wall Rough | In-wall plumbing | Fixture rough-in, venting, protection | | Equipment Set | Major equipment | Anchorage, isolation, clearances | | Insulation | Pipe/duct insulation | Before concealment, thickness, vapor barrier | | Pressure Test | Piping systems | Per code, witnessed, documented | | Ceiling Close-in | Before ceiling install | All work complete, access panels | | TAB | After system operational | Balanced, documented, meets design | | Final | Before occupancy | Fixtures complete, operational | → See [code-compliance.md](references/code-compliance.md) for code requirements and [testing-balancing.md](references/testing-balancing.md) for testing procedures. ### Common Pressure Test Requirements | System | Test Pressure | Duration | Medium | |--------|---------------|----------|--------| | Domestic Water | 1.5x working (min 125 psi) | 2 hours | Water | | Chilled Water | 1.5x working (min 150 psi) | 2-4 hours | Water | | Hot Water | 1.5x working (min 150 psi) | 2-4 hours | Water | | Steam | 1.5x working | 2-4 hours | Air/water | | DWV (water test) | 10 ft head minimum | 15 minutes | Water | | DWV (air test) | 5 psi | 15 minutes | Air | | Natural Gas | 1.5x working (min 3 psi) | Per AHJ | Air | | Medical Gas | 1.5x working (min 150 psi) | 24 hours | Oil-free nitrogen | → See [testing-balancing.md](references/testing-balancing.md) for complete testing procedures. ### MEP Coordination Priority (Top to Bottom in Ceiling) | Priority | System | Reason | |----------|--------|--------| | 1 | Plumbing drains | Gravity-dependent, must maintain slope | | 2 | Ductwork | Large cross-section, limited flexibility | | 3 | Cable tray/conduit | Can route around obstacles | | 4 | Fire protection | Some flexibility, but needs head clearance | | 5 | HVAC piping | Pressure system, can offset vertically | | 6 | Plumbing supply | Pressure system, most flexible | → See [coordination-sequencing.md](references/coordination-sequencing.md) for BIM coordination and sequencing. ### Installation Sequence (Typical) | Phase | Activities | Duration Impact | |-------|------------|-----------------| | Underground | Below-slab drains, sleeves, equipment pads | Critical path | | Slab on Grade | Underslab inspection, pour coordination | Hold point | | Overhead Rough | Main distribution, hangers, equipment set | Longest phase | | Wall Rough | Risers, branch piping, fixture carriers | Parallel with overhead | | Equipment Start | Major equipment installation and piping | After structure complete | | Insulation | All piping and duct insulation | Before close-in | | Trim | Fixtures, diffusers, controls | After finishes | | TAB/Commissioning | Testing, balancing, commissioning | Before occupancy | ### Safety Hazards Quick Reference | Hazard | Key Controls | Permits/Certifications | |--------|--------------|------------------------| | Confined Space | Entry permit, attendant, rescue plan | Confined space permit | | Hot Work | Fire watch, permit, clear area | Hot work permit | | Refrigerants | EPA 608 certified technicians | EPA 608 certification | | Heavy Lifts | Rigging plan, certified operators | Crane permit | | Heights | Fall protection >6 ft | Competent person | | Trenching | Shoring >4 ft, competent person | Excavation permit | | Steam/Hot Water | Lockout/tagout, PPE | LOTO procedures | → See [safety-hazards.md](references/safety-hazards.md) for complete safety requirements. ## Reference Documents ### Equipment & Systems - [HVAC Equipment](references/hvac-equipment.md) - AHUs, chillers, boilers, cooling towers, pumps, VFDs - [Ductwork & Distribution](references/ductwork-distribution.md) - Duct types, construction, dampers, terminals, diffusers - [HVAC Piping Systems](references/piping-systems-hvac.md) - Chilled water, hot water, steam, refrigerant, valves - [Plumbing Fixtures & Drainage](references/plumbing-fixtures-drainage.md) - Fixtures, DWV, grease interceptors, testing - [Plumbing Water Systems](references/plumbing-piping-water.md) - Domestic water, water heaters, backflow, testing - [Specialty Systems](references/specialty-systems.md) - Medical gas, lab, compressed air, natural gas coordination ### Installation Requirements - [Insulation Requirements](references/insulation-requirements.md) - Pipe and duct insulation, vapor barriers, thickness - [Testing & Balancing](references/testing-balancing.md) - Pressure tests, TAB procedures, commissioning - [Controls & Sequences](references/controls-sequences.md) - BAS, sequences of operation, points lists ### Compliance & Coordination - [Code Compliance](references/code-compliance.md) - IMC, IPC, ASHRAE, NFPA, inspections - [Coordination & Sequencing](references/coordination-sequencing.md) - MEP coordination, routing priority, sequencing, BIM - [Safety Hazards](references/safety-hazards.md) - Confined space, hot work, rigging, refrigerants - [Specifications & CSI](references/specifications-csi.md) - Division 22/23, key sections, common issues ## Related Skills - **construction-safety-management** - General safety, OSHA requirements, JHA/JSA procedures - **vdc-bim-coordination** - Clash detection, LOD requirements, model coordination - **procore-project-management** - RFI, submittal, and daily log workflows - **schedule-management-cpm** - Activity sequencing, schedule impacts, critical path - **quality-control-closeout** - QC procedures, commissioning, closeout documentation ## Field Problem-Solving Guide ### Common Issues & Solutions | Issue | Likely Cause | Solution | |-------|--------------|----------| | No flow in hydronic system | Air bound, closed valve, pump issue | Check air separator, valve positions, pump rotation | | Insufficient airflow | Duct obstruction, damper closed, dirty filter | Walk duct route, check damper positions, inspect filter | | Drain backup | Blockage, improper slope, missing vent | Camera inspect, check slope, verify venting | | Water hammer | Quick-closing valve, no arrestor | Install arrestor, adjust valve closing speed | | Condensation on pipes | Missing/damaged insulation, vapor barrier breach | Repair insulation, seal vapor barrier |