By ZENTVO Engineering Team. ZENTVO designs modular water storage systems for potable water, fire reserve, municipal supply and industrial utility water, with engineering review before tank layout, nozzle position and fabrication drawings are released.
A water tank nozzle schedule is the table that tells the tank supplier every required connection: inlet, outlet, overflow, drain, vent, manhole, level instrument, fire suction, sampling point and spare nozzle. It should state the nozzle tag, service, size, flange standard, elevation, orientation, material, gasket, reinforcement and matching pipe connection. Without it, a tank quotation is only a volume estimate, not an installation-ready proposal.
For early RFQs, start with this rule: size the inlet and outlet from design flow, make the overflow no smaller than the inlet unless the hydraulic calculation proves otherwise, place the drain at the lowest practical point, and give every nozzle an elevation from the tank floor or finished foundation level. For a Stainless Steel Bolted Water Tank, the nozzle schedule should be approved before panel fabrication.
Six fabrication rules to lock before pricing a tank
Nozzle Schedule Template
A usable nozzle schedule gives the fabricator enough information to place, reinforce and label each tank opening.
Source: the template below is ZENTVO RFQ guidance for modular water tanks; final sizes and elevations should follow the piping design, tank drawing and project standard.
| Tag | Service | Size range | Typical location | Elevation rule | Notes |
|---|---|---|---|---|---|
| N1 | Inlet | DN50–DN200 | Upper side wall or roof | Above normal water level or with approved inlet arrangement | Add air gap or backflow control where required |
| N2 | Outlet | DN80–DN250 | Lower side wall | Usually 150–300 mm above floor unless full drainable design is required | Coordinate with pump suction and usable volume |
| N3 | Overflow | DN100–DN300 | Upper side wall | Set at maximum operating water level | Route to visible safe discharge |
| N4 | Drain | DN50–DN150 | Lowest practical point | At floor level or sump | Valve access and safe discharge are mandatory |
| N5 | Vent | DN80–DN250 | Roof or high side wall | Above overflow level | Add insect screen and weather protection |
| N6 | Manhole | 600 × 600 mm or circular equivalent | Roof or side wall | Accessible from platform or floor | Needed for cleaning and inspection |
| N7 | Level instrument | DN25–DN80 | Side wall or roof | Matched to instrument range | Separate from turbulent inlet zone |
| N8 | Fire suction | DN150–DN300 | Lower side wall or suction chamber | Per fire pump hydraulic design | Confirm NFPA 22 or local fire code if applicable |
| N9 | Sampling point | DN15–DN25 | Outlet zone or recirculation line | Operator-accessible height | Useful for potable commissioning and water-quality checks |
| N10 | Spare nozzle | DN50–DN150 | Blank flanged connection | Match future tie-in plan | Cheaper before fabrication than after installation |
This is a planning table, not a universal design code. A municipal potable tank, a factory cooling-water tank and a Fire Water Storage Tank do not need the same nozzle schedule.
What Each Nozzle Does
Each nozzle controls a different risk: filling, withdrawal, overflow protection, cleaning, air movement, access or instrumentation.
Source: the outlet, drain, overflow and vent values in this section are ZENTVO preliminary layout rules for RFQ drawings; final dimensions should follow the approved piping and tank drawings.
Inlet Nozzle
The inlet nozzle brings water into the tank without creating avoidable turbulence, short-circuiting or backflow risk.
Place the inlet where incoming water mixes without striking a wall seam, gasket line or level instrument. For potable tanks, the inlet arrangement should follow the local backflow rule and water authority requirement. If the inlet is located below maximum water level, the piping designer must address backflow prevention and isolation.
Outlet Nozzle
The outlet nozzle controls usable volume because its elevation decides how much water remains below the outlet.
For building and utility tanks, place the outlet invert 150–300 mm above the tank floor when sediment control and pump protection are needed. For full drainable process tanks, the outlet and drain arrangement should be different: the service outlet feeds the process, and the drain removes the final low-level water during cleaning.
Overflow Nozzle
The overflow nozzle protects the tank from uncontrolled filling and should discharge to a visible safe point.
Use a larger overflow when the inlet flow is uncertain, the fill valve is automatic, or the tank is connected to a high-flow municipal or pump line. A common RFQ rule is overflow diameter ≥ inlet diameter, then the hydraulic engineer confirms final capacity, screen loss and discharge route.
Drain Nozzle
The drain nozzle makes cleaning possible because it removes water and sediment from the lowest practical point.
A drain placed 100 mm above the floor leaves sediment behind. A drain hidden under pipework slows maintenance and creates safety risk. Put the drain valve where an operator can reach it, and state the discharge route so cleaning water does not flood the foundation or plant room.
Vent Nozzle
The vent nozzle prevents pressure or vacuum during filling and drawdown.
For atmospheric tanks, vent free area should be matched to expected inflow and outflow. As an early ZENTVO screening rule, keep screened vent free area at least equal to the largest overflow flow area unless the piping design gives a larger requirement. A blocked vent leads to roof deformation, slow filling, pump suction problems or air noise.
Flow Calculation Example
Nozzle size should be checked with flow velocity before the drawing is frozen.
Source: this example uses the continuity equation velocity = flow / area for preliminary RFQ screening; final nozzle size should follow the piping engineer’s pressure-loss and transient analysis.
Assume a tank outlet must deliver 50 m³/h to a pump line.
v = Q / A = 0.0139 / 0.00785
Location and Elevation Rules
Nozzle elevation should be dimensioned from a clear datum, usually tank floor level, finished foundation level or tank centerline.
Source: the dimensional values below are ZENTVO layout rules for RFQ drawings; project drawings and local piping standards control final dimensions.
| Connection | Recommended datum | Starting elevation rule | Main risk if missed |
|---|---|---|---|
| Inlet | Tank floor or roof level | Above normal operating water level where the design uses free discharge | Backflow, turbulence, short-circuiting |
| Outlet | Tank floor | 150–300 mm above floor for sediment allowance | Dead volume or sediment intake |
| Overflow | Tank floor | At maximum operating water level, below roof structure | Hidden overfill or roof flooding |
| Drain | Tank floor | Lowest practical point, with fall to discharge | Incomplete cleaning |
| Vent | Roof or high side wall | Above overflow level | Vacuum, pressure, screen blockage |
| Manhole | Roof or side wall | Accessible with 600–1,000 mm working clearance | Unsafe inspection access |
| Fire suction | Tank floor | Per pump NPSH and fire design | Vortexing or unusable fire volume |
The datum belongs in the schedule. A note that says “outlet low level” is not enough for fabrication; write “N2 outlet centerline 300 mm above internal floor” or the equivalent project datum.
Standards and Approval References
The nozzle schedule should name the standards that control flanges, tank design, potable contact, fire service and disinfection.
| Reference | Where it applies |
|---|---|
| ASME B16.5 | Flange dimensions, pressure-temperature ratings, tolerances and marking from NPS ½ to NPS 24.1 |
| AWWA D103 | Bolted steel water tank design, construction, inspection and testing where specified.2 |
| AWWA C652 | Disinfection planning for potable-water storage facilities after construction or maintenance.3 |
| NFPA 22 | Water tanks for private fire protection where the fire system requires NFPA 22.4 |
| NSF/ANSI 61 / NSF/ANSI/CAN 61 | Health-effects evaluation for drinking-water-contact components.5 |
| WRAS BS 6920 | UK water-contact testing route for materials used with wholesome water.6 |
| ISO 9001 | Quality management framework for document control, inspection and corrective actions.7 |
Do not use a standard name as decoration. If the schedule names ASME B16.5 Class 150, then the flange face, bolt pattern and mating pipe flange must match that class. If the schedule names NSF/ANSI 61, then the wetted nozzle lining, gasket and sealant should be inside the certification scope.
Common Nozzle Schedule Mistakes
Most nozzle errors happen before manufacturing because the RFQ lacks datum, flow and connection standard.
Avoid these mistakes:
- Listing “inlet and outlet included” without DN size, flange class or location.
- Placing the outlet too low, which pulls sediment into the pump line.
- Placing the overflow where discharge is hidden, which hides valve failure.
- Omitting a vent on an atmospheric tank, which creates pressure or vacuum during operation.
- Using a side manhole that cannot be reached after the tank is installed.
- Putting level sensors in the inlet turbulence zone, which causes unstable readings.
- Treating fire suction like a normal domestic outlet even when NFPA 22 or local fire rules apply.
- Forgetting a sampling point for potable commissioning and routine water-quality checks.
One ZENTVO project-screening example for a 100 m³ tank found that moving a DN150 outlet from 100 mm to 300 mm above the floor preserved pump protection while keeping more than 97 m³ of usable operating volume. The important lesson is not the exact number; it is that nozzle elevation changes both hydraulic function and usable volume.
RFQ Input List and Specification Checklist
A complete RFQ gives the nozzle schedule before the tank is priced, drawn and fabricated.
Send these items with the inquiry:
- Tank capacity and dimensions in m³, mm or litres.
- Tank material: stainless steel, coated steel, galvanized steel, pressed steel, GRP/FRP or glass-fused-to-steel.
- Water duty: potable, fire reserve, industrial utility, municipal, rainwater or process water.
- Design flow for each nozzle in m³/h or L/s.
- Nozzle tag list: inlet, outlet, overflow, drain, vent, manhole, instrument, sampling and spare.
- Flange standard and class: ASME B16.5 Class 150, DIN, EN, JIS or project-specific.
- Elevation datum: tank floor, finished foundation, centerline or site coordinate.
- Required standards: AWWA D103, AWWA C652, NFPA 22, NSF/ANSI 61, WRAS BS 6920, ISO 9001 or local code.
- Pipe material and corrosion requirements for wetted components.
- Installation constraints: wall clearance, platform access, pipe supports and valve access.
For fabrication-ready support, send your project requirements through the ZENTVO contact page with the tank volume, flow rates and nozzle list. ZENTVO can return a preliminary drawing, nozzle schedule and material recommendation for Installation Guidelines review.
Frequently Asked Questions
Source: FAQ values summarize the nozzle schedule, flow calculation and standards guidance in this article.
What is a water tank nozzle schedule?
A water tank nozzle schedule is a table listing every tank connection by tag, service, size, flange standard, location, elevation, material and notes. It tells the tank fabricator where to place inlet, outlet, overflow, drain, vent, manhole, instrument and sampling connections before panels are manufactured.
What size should a water tank overflow nozzle be?
The overflow nozzle should be no smaller than the inlet as an early RFQ rule, then confirmed by hydraulic calculation. For example, a DN100 inlet often leads to a DN100 or DN150 overflow starting point. High-flow automatic filling or screened discharge usually pushes the overflow larger.
Where should the outlet nozzle be placed on a water tank?
The outlet nozzle is commonly placed 150–300 mm above the tank floor when sediment control and pump protection matter. Full-drain process tanks need a separate drain at the lowest practical point. State the exact outlet centerline elevation from the tank floor or finished foundation datum.
Does a water tank need a vent nozzle?
An atmospheric water tank needs venting so filling and drawdown do not create pressure or vacuum. As an early screening rule, keep screened vent free area at least equal to the largest overflow flow area unless the piping design gives a larger value. Add insect screen and weather protection.
Which standards apply to water tank nozzles?
Common references include ASME B16.5 for flanged connections, AWWA D103 for bolted steel tank design, NFPA 22 for private fire-protection tanks, NSF/ANSI 61 for drinking-water-contact components, WRAS BS 6920 for UK potable contact, and AWWA C652 for potable-tank disinfection.
Author and Review Record
Written by ZENTVO Engineering Team, a water-storage engineering group focused on modular tank layout, nozzle positioning, installation coordination and project-specific material selection.
Review scope: nozzle schedule template, flow calculation, datum rules, standards references, RFQ inputs and fabrication risks.
Sources
- ASME B16.5 — Pipe Flanges and Flanged Fittings. Covers pressure-temperature ratings, materials, dimensions, tolerances, marking and testing for pipe flanges and flanged fittings.
- AWWA — Storage Standards. AWWA D103 covers design, construction, inspection and testing of new bolted carbon steel tanks for water storage.
- AWWA C652 — Disinfection of Water Storage Facilities.
- NFPA 22 — Standard for Water Tanks for Private Fire Protection.
- NSF/ANSI/CAN 61 — Testing and Certification. Health-effects benchmark for products and materials in contact with drinking water.
- WRAS BS 6920 — Testing Requirements. UK water-contact testing for materials used with wholesome water.
- ISO 9001 — Quality Management Systems. Document control, inspection and corrective-action framework.