1. Prepare the inputs

For an existing model, open Prepare network, expand “Import an existing PFD or MDX model”, and choose a file up to 80 MB. Select Read model if inspection does not start automatically. Review the detected networks and their pipe and manhole schedules. Imported geometry is read-only in the map.

Check coordinates, ground levels, pipe connectivity, flow direction and model units against the source model. A cover level is the elevation at the manhole surface; minimum cover is the depth of ground above a pipe crown. They are different inputs.

2. Or draw a new network

1. Open Prepare network and create a network with a descriptive name and type. Search for the site address or postcode on the map.
2. Select Draw pipe run. Click each manhole location in upstream-to-downstream order; click an existing manhole to connect to it. Press Esc to finish.
3. Select the terminal manhole and set its type to Outfall in Properties. Every route must lead to a terminal outfall. Loops and multiple downstream pipes from one node are not supported.
4. Select each node and enter its surveyed cover level. Auto ground levels is optional: it sends coordinates to Open Topo Data for approximate ASTER elevations. These roughly 30 m estimates require survey and datum checks.
5. Select Draw Area and click around a contributing catchment. Choose Finish Area, assign its receiving manhole and enter PIMP (the percentage impermeable area). Check areas and contributing flows in the schedules.
6. Choose IDF Matrix rainfall and a return period. Enter intensity in mm/hr for every duration in the selected return-period column. Drawn networks require this complete column.
7. Choose Use this network to move into the optimiser. Recommit after editing the network.

Use Select / move to edit geometry, or click a pipe to inspect its upstream and downstream ends and reverse flow. Undo and Redo recover recent edits. Save draft downloads editable JSON; Open draft loads it. Restore browser draft retrieves the last locally saved draft, when browser storage is available.

Inspecting 3D terrain

Switch to 3D terrain after adding or importing a network. Drag to orbit, Shift-drag to pan, and scroll to zoom. Fit network resets the view. Enter ground levels for a surface, or enable Auto ground levels and select Load online surface. Without sufficient data, an explanatory empty view appears. Imported pipes need end invert levels. Drawn pipes use illustrative 150 mm diameter and 1.2 m crown cover until calculated; this is not an optimised results viewer.

3. Confirm the design rules

The optimiser minimises total pipe length multiplied by average depth to invert. This favours shallower excavation across the network; it is not a priced construction-cost estimate. It can select a larger pipe where that reduces depth. Equally shallow designs favour smaller pipes, then fewer backdrops. The velocity setting is a minimum full-bore velocity, not a maximum or a promise of actual partial-flow velocity.

Open Optimise and select the networks to process. Review the minimum cover, velocity, gradient and diameter settings for the specific design. Confirm each network's optimisation mode and any fixed downstream level. Expand the specialist settings only where needed: fixed levels, fixed diameters, pipe-specific cover, backdrop and service constraints must match the project requirements. Minimum and maximum backdrop values set the permitted drop at a manhole. All permitted backdrop locations are considered together with the other constraints; a separate depth trigger is no longer needed.

Service crossings change pipe levels, not its route in plan. Enter chainage from the upstream end, the service invert level in the model datum, its diameter and the required clear gap. Above and Below refer to the drainage pipe. With the service above it, the gap is from drainage soffit to service invert. With the service below it, the gap is from service soffit to drainage invert. Auto compares both positions as part of the whole-network design. Pipe gradients and diameters can change to meet the constraints. Conflicts with fixed levels or cover stop the run. Check the downloaded model and log; the Prepare network map shows the input geometry.

Circular manholes are sized automatically from the largest final connected pipe, including laterals, using Water UK DCG Table B1 for adoptable sewers in England. The exported model and manhole schedule show the selected internal diameter; the schedule includes mm and m units. Locked chambers retain their size and must meet the minimum. Outfalls and specialist structures are retained. Check schedule notes for junction benching, backdrops and access details that may require larger chambers.

Read the engineering notice immediately above Run optimisation, then start the run once the inputs are complete. Keep the page open while progress appears in the result log. If validation fails, correct the named field or model issue before retrying.

4. Download, compare and check

When the run finishes, download the available model, pipe and manhole schedules, and change report. Compare the changes with the original design. Check connectivity, diameters, inverts, cover, gradients, velocities, constraints and constructability, then open the exported model in the source design software for further hydraulic checks.

A failed run provides a diagnostic log. Model downloads are available only after the final checks pass. All outputs need review by a suitably qualified civil engineer before use.

Optional recent-run storage retains the last five private run links on this device. It does not back up the files. Server restarts or retention changes may make links unavailable; download important results. Clear saved access by unticking the option.

Capabilities and limits

HydroOptimiser applies configured rules to gravity drainage networks and produces reviewable models and schedules. Drawn-network sizing uses IDF rainfall and cumulative Rational Method flows. The geometry optimiser uses the supplied design flows and the existing circular full-bore hydraulic model. It solves levels, catalogue diameters, service clearances and permitted manhole crown drops together, then verifies the final geometry and exported file. The optimum applies to this excavation-depth objective and supplied flow envelope.

It does not recalculate rainfall or partial-flow travel times after geometry changes, check cover along an intermediate ground profile, or perform dynamic storm simulation, verify a site survey, certify regulatory compliance, design pressurised plumbing systems or replace independent hydraulic and engineering checks. Terrain interpolation is an illustration, not a measured survey.

When something needs attention

• Blank map: check the connection and map service availability; use the schedules to inspect data.
• No 3D geometry: add a network, check ground and invert levels, then select Fit network.
• Unavailable dropdown: no alternative selection exists yet. Add or load the relevant network or pipes first.
• Missing rainfall: complete every duration for the selected return period.
• Run or download unavailable: retry the connection, use the saved run link if available, or re-upload the original model. Contact support with the job reference and error text.