01
Connection constraints
Fix inverts, connection points and the levels the whole system has to work back from. Everything else is downstream of this.
Plumbing, public health and drainage BIM services
The only discipline on the project that cannot be rerouted around a problem, because gravity is not negotiable — which makes it the one that should be routed first and almost never is.
Public health
The engineering position
Gravity sets the sequence, so gravity should set the routing order
A soil stack has one place it can be. A drainage run has a required fall, a maximum length before an access point, and a fixed invert at the connection. None of those are negotiable in the way a cable tray route is. On projects where drainage is routed after mechanical and electrical, the resolution is almost always a pumped solution nobody budgeted for, or a dropped ceiling nobody wanted. We route the gravity systems first.
Falls have to be modelled, not annotated
A drainage run drawn flat with a note saying "1:80 fall" cannot be coordinated. It does not clash where it will actually be, and it does not tell you that the invert at the far end is below the slab. Modelling the fall is more work at authoring and very much less work at coordination, which is the same trade the rest of this practice is built on.
Connectivity is what makes the model checkable
Public health is where broken connectivity hides most easily: a run that looks continuous in a 3D view but is three disconnected segments to the software. Authoring with connectivity intact is what lets a routine follow a run from appliance to connection and tell you it does not actually get there.
Deliverables
What is actually produced and issued
Any of these can be appointed on their own or combined. Nothing here depends on buying the intelligence layer, which is not for sale in any case.
DeliverableAbove-ground drainage
Soil, waste and vent modelled with falls, access points and connectivity intact.
DeliverableBelow-ground drainage
Runs, inverts, chambers and connections coordinated against foundations and other buried services.
DeliverableDomestic cold and hot water
Distribution, boosting, storage and return, sized and modelled with system assignment.
DeliverableRainwater and syphonic systems
Roof drainage and downpipe routing coordinated with structure and facade.
DeliverableSanitaryware and appliance schedules
Scheduled from the model against the architectural room data.
DeliverablePipe sizing and discharge calculations
Sized against the modelled network with the loading units and method stated.
How it runs
The sequence, and why it is in this order
Sequence is not a formality on this kind of work. Most of the expensive rework we are asked to fix was produced by doing step four before step two.
02
Stack and riser positions
Agreed with the architect early, because they are the hardest thing on the project to move.
03
Gravity routing
Above and below ground, modelled with true falls and access points at the required intervals.
04
Pressurised systems
Domestic water, boosting and hot water return, routed and sized against the gravity systems already fixed.
05
Coordination
Federated testing against structure and the other services, with access chamber and rodding access clearance included.
06
Documentation
Drawings, schedules and calculations, QA rule set run, engineer signs.
What we need to start
The inputs that decide whether a start is a real start
Missing any of these is survivable. Not knowing which of them are missing is not, so we establish it at enquiry stage rather than at forty per cent.
- Architectural model with sanitary layouts and room data
- Structural model with slab levels, foundations and any existing below-ground constraints
- Connection points, invert levels and the adopted sewer arrangement
- Water supply pressure and any storage or boosting requirement
- The drainage standard the project runs to
Automation
Where automation applies to this work
Every line carries its real status. Three of the four states on this site mean "not yet", and we use them.
AutomationConnectivity and continuity checkingLive
Every run traced from appliance to connection as a graph, so a visually continuous but disconnected system is caught at authoring rather than at coordination.
AutomationFall and gradient validationLive
Modelled gradient tested against the required fall for the pipe size, run by run, with failures listed by element.
AutomationAccess point spacing rulesLive
Rodding and access point intervals tested as a rule along each run.
AutomationInvert clash against structureLive
Below-ground runs tested against foundations and slab levels as part of the federated rule set.
Scope boundary
What this appointment does not include
Published because a scope boundary discovered at month three is a dispute, and the same boundary stated at enquiry stage is just information.
- We do not carry out drainage adoption applications or negotiate with the adopting authority.
- We do not perform CCTV survey or condition assessment of existing drainage.
- We do not certify compliance with a jurisdiction's plumbing code; we design to the standard you name and your engineer of record certifies.
FAQ
Questions we are asked at enquiry stage
Do you model drainage with real falls?
Yes, as a matter of course. A flat run with a fall annotation cannot be coordinated and will produce a coordination report that is wrong in the one discipline where being wrong is most expensive to fix.
Can you coordinate below-ground drainage against foundations?
Yes. It is part of the federated rule set rather than a separate exercise, and invert-against-foundation is one of the checks that most often finds something.
Which sizing method do you use?
Discharge unit or loading unit methods to the standard the project names, with the method and the assumed simultaneity stated on the output rather than implied.
What if the drainage connection level is not yet known?
We model to a stated assumed invert and flag it as an assumption on the issue. What we will not do is pick a level quietly, because every run in the building is dimensioned back from it.
Related
Where this connects
Full MEP engineeringAll four disciplines coordinated together.
BIM coordinationGravity systems tested against structure and everything else.
HealthcareWhere drainage, clearance and validation requirements are at their strictest.
Residential and mixed useRepeated riser typologies — the ideal condition for rule-based checking.