22 KiB
22 KiB
Water System Specification — POE Reverse Osmosis + Stainless Steel Distribution
1. Design Philosophy
The same principle that governs the air system applies to water: control every parameter, make it measurably better than the municipal supply — not merely acceptable, but actively health-positive.
- Point of Entry (POE): Every drop of water in the house passes through the treatment system. Not a single-tap under-sink filter — whole-house purification. Drinking, cooking, showering, and appliances all receive treated water.
- Reverse Osmosis: Removes 95-99% of dissolved solids including heavy metals, nitrates, pharmaceuticals, PFAS, and microplastics. The only residential technology that achieves near-laboratory water purity.
- Stainless Steel (316L): RO water is demineralized and slightly acidic (pH ~6.5 before remineralization). It would aggressively corrode copper pipes, leaching copper into the water. 316L stainless steel is completely inert, food-grade, and has zero leaching. Press-fit connections eliminate solder flux contamination.
- Ceiling routing: Supply plumbing runs in the Plafotherm suspended ceiling void — accessible by removing a ceiling panel. Same maintainability principle as the raised floor for electrical and data. No pipes buried in walls or screed. A leak is found and fixed in minutes, not days.
- Drain/waste routing: Gravity-dependent waste pipes route in the raised floor cavity (ground floor) and vertical risers. Not in the ceiling void.
The water system is not a luxury filter. It is a controlled treatment chain that produces verified, monitored, food-grade water at every outlet in the house.
2. Water Treatment Chain
flowchart TD
A["Municipal Water Supply\nBremen/Grasberg mains"] --> B
B["Motorized Master Shut-off\n316L ball valve, KNX-controlled"] --> C
C["Stage 1: Sediment Pre-filter\n20 um + 5 um cartridges"] --> D
D["Stage 2: Activated Carbon\nChlorine, VOC, taste/odor removal"] --> E
E["Booster Pump\nVariable speed, 5-6 bar output"] --> F
F["Stage 3: RO Membrane Bank\n95-99% TDS rejection"] --> G
G["Stage 4: Remineralization\nCalcite + corosite, pH 7.0-7.5"] --> H
H["Stage 5: UV Sterilization\n254 nm, 40 mJ/cm2 minimum"] --> I
I["Buffer Tank\n200-300L 316L stainless steel"] --> J
J["Distribution Pump\nVariable speed, maintains 3-4 bar"] --> K
K["316L Stainless Steel\nCeiling Distribution"]
F -->|"Reject Water\n25-50% of feed"| RJ["Garden Irrigation\nor Drain"]
style F fill:#1a3d5e,color:#fff
style H fill:#1a5e1a,color:#fff
style B fill:#8b0000,color:#fff
2.1 Stage Details
| Stage | Function | Media/Element | Change Interval | Initial Delta-P |
|---|---|---|---|---|
| 1 | Sediment removal | 20 um + 5 um spun polypropylene | Every 3-6 months | 20-40 kPa |
| 2 | Chlorine + VOC removal | Granular activated carbon (GAC) | Every 6-12 months | 30-50 kPa |
| 3 | Dissolved solids removal | TFC polyamide RO membranes | Every 2-3 years | 100-200 kPa |
| 4 | Mineral addition | Calcite + corosex mixed media | When pH drops below 7.0 | Negligible |
| 5 | Bacterial sterilization | UV-C lamp, quartz sleeve | Annual lamp replacement | N/A |
2.2 Critical Design Rules
- Carbon BEFORE RO: Chlorine destroys RO membranes. The activated carbon stage must remove all free chlorine before water reaches the membranes. This is non-negotiable.
- Remineralization AFTER RO: Pure RO water (TDS 5-20 mg/L) is too aggressive for any metal contact and lacks essential minerals. Remineralization raises pH to 7.0-7.5 and adds calcium/magnesium for health and pipe protection.
- UV AFTER storage: The buffer tank is a potential bacterial growth site. UV sterilization must be the final treatment before distribution.
- Booster pump BEFORE RO: RO membranes require 4-6 bar feed pressure for adequate rejection. Municipal pressure alone (3-4 bar typical) is insufficient.
3. RO System Sizing
| Parameter | Specification |
|---|---|
| Household size | 4 persons |
| Daily consumption (all uses) | 300-500 L/day |
| Peak demand | 20-30 L/min (multiple fixtures simultaneous) |
| RO rated capacity | 500-800 L/day (oversized for peak and membrane aging) |
| Recovery ratio | 50-75% (with concentrate recirculation) |
| Reject water volume | 125-250 L/day (plumbed to garden irrigation) |
| Feed water pressure | 5-6 bar (via booster pump) |
| Permeate TDS | 5-20 mg/L (before remineralization) |
| Membrane type | TFC (Thin Film Composite) polyamide |
| Number of membranes | 2-4 (parallel, commercial 4040 format) |
Note: Under-sink residential RO units (50-100 GPD) are far too small for whole-house use. This requires a commercial/light-industrial system with 4040-format membrane housings, a dedicated booster pump, and a properly sized buffer tank.
4. Equipment Specifications
| Component | Specification | Location |
|---|---|---|
| RO unit | Commercial-grade, multi-membrane, 316L frame | Technical room |
| Pre-filter housings | 20" Big Blue, tool-free cartridge change | Technical room |
| Remineralization vessel | 10" x 54" FRP tank, calcite + corosex media | Technical room |
| UV sterilizer | 316L chamber, quartz sleeve, intensity monitor | Technical room |
| Buffer tank | 200-300L, 316L stainless steel, atmospheric or diaphragm | Technical room |
| Booster pump | Variable speed, 316L head, < 45 dB(A) | Technical room |
| Distribution pump | Variable speed, pressure-maintaining, < 40 dB(A) | Technical room |
| Master shut-off valve | 316L motorized ball valve, fail-closed, KNX | Water entry point |
Technical room sizing: The water treatment equipment requires approximately 2-3 m2 of floor space plus the buffer tank. The technical room must be expanded from 4-6 m2 (air system only) to 8-10 m2 to accommodate both air and water systems. See 03-baufritz-coordination-spec Section 2.
5. Stainless Steel Plumbing
5.1 Material Specification
| Parameter | Specification |
|---|---|
| Grade | AISI 316L (EN 1.4404) |
| Standard | DIN EN 10312 (stainless steel tubes for water) |
| Approval | DVGW W 541 (drinking water) |
| Internal surface | Electropolished or bright-annealed |
| Wall thickness | 1.0-1.5 mm (per DIN EN 10312) |
Why 316L, not 304: 316L contains 2-3% molybdenum, providing superior resistance to chloride-induced pitting and crevice corrosion. RO permeate, while low in chlorides, is aggressive due to low pH and mineral content. 316L provides the maximum safety margin for a lifetime installation.
Why not copper: RO water (pH 6.0-6.5 before remineralization, TDS < 20 mg/L) is classified as "aggressive water" per DIN 50930-6. It would dissolve copper from pipes, exceeding the 2 mg/L limit within months. Even with remineralization, 316L eliminates any leaching risk entirely.
5.2 Connection System
| Parameter | Specification |
|---|---|
| System | Press-fit (Viega Sanpress Inox or Geberit Mapress Stainless Steel) |
| Fitting material | 316L stainless steel |
| O-ring material | EPDM (food-grade, KTW/W270 drinking water approved) |
| Press tool | Standard Viega or Geberit press jaw |
| Joint type | Permanent, no re-tightening required |
No soldering: Solder flux residue contaminates water and creates internal surface irregularities where biofilm accumulates. Press-fit is clean, fast, and permanent.
No threaded connections: Thread sealant (PTFE tape, hemp, paste) can harbor bacteria and degrade over time. Press-fit O-rings provide a clean, food-grade seal.
5.3 Pipe Sizes
| Function | Outer Diameter | Nominal Width | Insulation OD |
|---|---|---|---|
| Main distribution (from manifold) | 28 mm | DN25 | ~54 mm |
| Branch to rooms/zones | 22 mm | DN20 | ~48 mm |
| Final connections to fixtures | 15 mm | DN12 | ~37 mm |
| Hot water recirculation | 15 mm | DN12 | ~41 mm |
5.4 Insulation
| Pipe Type | Insulation Thickness | Material | Purpose |
|---|---|---|---|
| Hot water supply | 13 mm | Closed-cell elastomeric (Armaflex HT) | Energy conservation, burn prevention |
| Cold water supply | 9 mm | Closed-cell elastomeric (Armaflex AF) | Condensation prevention in ceiling void |
| Hot water recirculation | 13 mm | Closed-cell elastomeric (Armaflex HT) | Energy conservation |
- All insulation continuous — no gaps at fittings (use pre-formed fitting covers)
- Vapor-tight joints on cold water insulation (prevents condensation inside insulation)
- Insulation must be UV-resistant if any sections are exposed
6. Distribution Architecture — Ceiling Routing
6.1 Manifold System
| Parameter | Specification |
|---|---|
| Material | 316L stainless steel |
| Location | Technical room wall, accessible |
| Configuration | Separate hot and cold manifolds |
| Per-branch features | Individual shut-off valve + flow meter |
| Monitoring | Flow data to Home Assistant via KNX/Modbus |
Each branch serves one zone (kitchen, bathroom 1, bathroom 2, utility, etc.). Individual shut-off allows isolating any zone for maintenance without affecting the rest of the house.
6.2 Ceiling Void Routing
Supply pipes run in the Plafotherm suspended ceiling void alongside existing services:
flowchart TD
subgraph CV["Ceiling Void Cross-Section (300 mm)"]
A["Structural Ceiling Deck (top)"]
B["MVHR Supply Trunk\n200-250 mm diameter"]
C["Plafotherm Heating Pipes\nDN 13, multiple runs"]
D["Hot Water Supply\n28 mm OD + 13 mm insulation"]
E["Cold Water Supply\n28 mm OD + 9 mm insulation"]
F["Plafotherm Suspension Profiles\n30-70 mm"]
G["Plafotherm Ceiling Panel (bottom)\n30-50 mm radiant panel"]
end
A --> B
B --> C
C --> D
D --> E
E --> F
F --> G
style B fill:#1a3d5e,color:#fff
style C fill:#8b0000,color:#fff
style D fill:#4a4a00,color:#fff
style E fill:#1a5e5e,color:#fff
Routing rules:
- Hot and cold mains run parallel, minimum 50 mm apart (thermal separation)
- Routed alongside (not crossing over) MVHR trunk duct where possible
- Where crossing is necessary, pipes pass below the MVHR trunk with clearance
- Pipe clamps: 316L stainless steel with EPDM isolation gasket (no galvanic contact with ceiling suspension steel)
- Minimum 20 mm clearance from MVHR ducts
- Drop-downs to fixtures through ceiling panel penetrations, sealed with airtight grommets (maintains house positive pressure)
- Every press-fit joint must be accessible by removing a Plafotherm ceiling panel — no joints hidden above permanent structure
Ceiling void capacity: The supply pipes (28 mm OD + 13 mm insulation = ~54 mm total diameter) are small relative to the MVHR trunk (200-250 mm). They fit within the existing 300 mm ceiling void allocation without increasing depth. No change to the room height budget (see 04-flooring-ceiling-spec Section 2).
6.3 Hot Water Recirculation
| Parameter | Specification |
|---|---|
| Loop material | 316L stainless steel, 15 mm OD |
| Insulation | 13 mm Armaflex HT |
| Pump | Low-watt circulation pump (5-10 W), 316L wetted parts |
| Control | Timer (active 06:00-23:00) + temperature sensor (activates when return temp drops below 45 C) |
| Target | Hot water at every tap within 5 seconds |
A recirculation loop eliminates water waste from running taps waiting for hot water. The loop runs from the hot water manifold through the furthest fixture branch and back to the water heater.
6.4 Vertical Risers
- Dedicated 316L stainless steel risers between floors
- Enclosed in accessible service shafts or boxed chases
- Fire-stop collars at all floor penetrations (DIN 4102)
- Accessible at both ceiling level (from below via ceiling panel) and floor level (from above via Doppelboden panel)
- Insulated to prevent condensation and heat loss
7. Drain and Waste Routing
Drain and waste pipes are gravity-dependent and route separately from supply:
| Location | Routing | Pipe Material | Notes |
|---|---|---|---|
| Ground floor | Doppelboden floor cavity (200 mm) | PP push-fit (Geberit Silent-PP) | Waste pipes 40-110 mm where cavity depth allows |
| Upper floor | Vertical drops through floor deck | PP push-fit | Horizontal runs in floor cavity below, not ceiling |
| Vertical stacks | Dedicated risers, boxed in | PP push-fit, 110 mm | Toilet waste, main stack |
| Kitchen | Grease trap before main drain | Stainless steel trap | Prevents grease buildup in drain |
| Bathroom | Standard DIN 1986 / EN 12056 sizing | PP push-fit | Waterproof membrane above floor panels |
No horizontal waste runs in the ceiling void: Waste pipes require gradient (1-2% fall per metre). Running them horizontally in the ceiling void would consume excessive depth and risk backup. All waste travels down, not sideways at ceiling level.
8. Hot Water Generation
| Parameter | Specification |
|---|---|
| Primary option | Indirect cylinder heated by main heat pump (same unit feeding Plafotherm ceiling) |
| Alternative | Dedicated heat pump water heater (COP 3-4) |
| Tank volume | 200-300 L |
| Tank material | 316L stainless steel inner |
| Storage temperature | 55-60 C (Legionella prevention per DVGW W 551) |
| Delivery temperature | 48 C at point of use (thermostatic mixing valves) |
| Anti-scald | Thermostatic mixing valves at all outlets |
| Legionella prevention | Weekly thermal disinfection to 70 C (automated, KNX-controlled) |
| Integration | KNX bus, Home Assistant monitoring (tank temp, energy, demand profile) |
Why 316L tank: The same logic as the pipes — RO-treated water (even remineralized) has lower mineral content than municipal water. Enamel-lined tanks can develop pinhole corrosion at enamel defects. 316L is immune to this failure mode and lasts the lifetime of the building.
9. Water Quality Targets
| Parameter | Target | Municipal Typical | RO Output (pre-remin) |
|---|---|---|---|
| TDS (Total Dissolved Solids) | 50-150 mg/L | 200-500 mg/L | 5-20 mg/L |
| pH | 7.0-7.5 | 7.0-8.5 | 6.0-6.5 |
| Hardness | 4-8 dH (soft) | 10-25 dH | < 1 dH |
| Free chlorine | 0 mg/L | 0.1-0.3 mg/L | 0 |
| Lead | < 1 ug/L | < 10 ug/L | < 1 ug/L |
| Copper | < 0.1 mg/L | < 2 mg/L | < 0.01 mg/L |
| PFAS (total) | < 2 ng/L | 2-20 ng/L | < 2 ng/L |
| Nitrate | < 5 mg/L | 10-50 mg/L | < 5 mg/L |
| Microplastics | 0 particles/L | Present | 0 |
| Bacteria (post-UV) | 0 CFU/mL | < 100 CFU/mL | 0 |
| Pharmaceutical residues | < 0.01 ug/L | 0.01-0.1 ug/L | < 0.01 ug/L |
10. Sensors and Monitoring
10.1 Inline Sensors
| Sensor | Location | Parameter | Protocol |
|---|---|---|---|
| TDS meter | Post-RO (before remin) | Membrane rejection health | 4-20mA / Modbus |
| TDS meter | Post-remineralization | Mineral dosing verification | 4-20mA / Modbus |
| pH sensor | Post-remineralization | pH correction verification | 4-20mA / Modbus |
| Flow meter | Per-branch at manifold | Consumption monitoring | Pulse / KNX |
| Flow meter | Total house | Total consumption | Pulse / KNX |
| Pressure sensor | Feed (pre-booster) | Municipal supply pressure | 4-20mA |
| Pressure sensor | Post-booster | Booster pump output | 4-20mA |
| Pressure sensor | Distribution | System pressure | 4-20mA |
| UV intensity | UV chamber | Sterilization dose verification | 4-20mA |
| Temperature | Hot water tank | Storage temperature | KNX |
| Temperature | Recirculation return | Loop efficiency | KNX |
10.2 Leak Detection
| Component | Specification |
|---|---|
| Leak sensors | Capacitive rope sensors at manifolds, under fixtures, ceiling void low points |
| Master shut-off | 316L motorized ball valve at POE, fail-closed, KNX-controlled |
| Auto shut-off triggers | Leak sensor activation, abnormal flow (continuous flow > 30 min without expected use), flow at 01:00-05:00 without manual override |
| Response time | Valve closes within 5 seconds of trigger |
| Manual override | Physical bypass valve for emergency (clearly labeled, sealed) |
10.3 Home Assistant Dashboard
| Widget | Data Source | Purpose |
|---|---|---|
| Water Quality Index | TDS + pH composite | At-a-glance water quality |
| RO Membrane Health | Post-RO TDS vs. feed TDS | Rejection rate %, replacement prediction |
| Daily Consumption | Flow meters | Per-branch and total usage |
| Hot Water Status | Tank temp + recirculation temp | Availability and efficiency |
| Leak Map | All leak sensors | Green/red per zone |
| Filter Status | Delta-P sensors + calendar | Remaining life per stage |
| UV Status | Intensity monitor | Lamp health |
10.4 Maintenance Alerts
| Condition | Alert Level | Action |
|---|---|---|
| Sediment pre-filter Delta-P > 2x initial | Warning | Plan filter change |
| Carbon pre-filter > 12 months | Warning | Replace cartridge |
| RO rejection rate < 95% | Warning | Monitor closely, plan membrane replacement |
| RO rejection rate < 90% | Critical | Replace membranes |
| Post-remin TDS < 50 mg/L | Warning | Replenish remineralization media |
| Post-remin pH < 7.0 | Warning | Replenish corosex media |
| UV intensity < 80% of nominal | Warning | Plan lamp replacement |
| UV intensity < 60% of nominal | Critical | Replace lamp immediately |
| Any leak sensor active | Critical | Auto shut-off + push notification + audible alarm |
11. Baufritz Coordination
11.1 Technical Room Expansion
The water treatment system requires the technical room to expand from 4-6 m2 (air system only) to 8-10 m2:
| Equipment | Floor Space | Notes |
|---|---|---|
| RO unit + pre-filters | ~1.0 m2 | Wall-mounted or floor-standing rack |
| Buffer tank (300L) | ~0.5 m2 | Floor-standing, 316L |
| Hot water cylinder (300L) | ~0.5 m2 | Floor-standing, 316L |
| Remineralization vessel | ~0.2 m2 | Floor-standing |
| UV sterilizer | ~0.1 m2 | Wall-mounted, inline |
| Access clearance | ~0.5 m2 | Front access for filter changes |
11.2 Additional Electrical Requirements
| Circuit | Rating | Purpose |
|---|---|---|
| RO booster pump | 230V / 16A | Variable speed pump |
| Distribution pump | 230V / 10A | Pressure-maintaining pump |
| UV sterilizer | 230V / 10A | UV lamp power supply |
| Recirculation pump | 230V / 10A | Hot water loop |
| Water sensors | 230V / 10A | TDS, pH, flow meters, leak sensors |
11.3 Construction Checkpoints
| Phase | Checkpoint |
|---|---|
| Framing | Ceiling void dimensions verified for water pipes alongside MVHR and Plafotherm |
| Framing | Service shaft / riser locations confirmed for vertical pipe runs |
| Pre-close | Municipal water entry point confirmed, drain for reject water available |
| Interior | Stainless steel ceiling runs installed and pressure-tested at 16 bar for 2 hours |
| Interior | All press-fit joints verified accessible via ceiling panel removal |
| Completion | RO system commissioned, TDS/pH verified at every outlet |
| Completion | Leak detection system tested (simulate leak, verify auto shut-off) |
| Completion | Flow meters calibrated, connected to Home Assistant |
12. Installation Sequence
flowchart TD
A["1. Install water entry point\nmunicipal connection to technical room"] --> B
B["2. Install RO system + buffer tank\nin technical room"] --> C
C["3. Install ceiling manifolds\nhot + cold, 316L"] --> D
D["4. Route stainless steel mains\nin ceiling void before Plafotherm panels"] --> E
E["5. PRESSURE TEST\n16 bar for 2 hours, all joints"] --> F
F["6. Install Plafotherm ceiling panels\ncovering pipe runs"] --> G
G["7. Install vertical risers\nand drop-downs to fixtures"] --> H
H["8. Route drain/waste\nin floor cavity and risers"] --> I
I["9. Install hot water cylinder\nconnect to heat pump circuit"] --> J
J["10. Connect all fixtures"] --> K
K["11. Flush entire system\nverify TDS and pH at every outlet"] --> L
L["12. Commission leak detection\ntest auto shut-off, connect to HA"]
style E fill:#1a5e1a,color:#fff
style K fill:#1a5e5e,color:#fff
style L fill:#1a5e5e,color:#fff
Key checkpoints (colored in diagram):
- Step 5: Pressure test at 16 bar — must pass before ceiling panels are installed over pipe runs
- Step 11: Water quality verification — TDS and pH must meet targets at every outlet
- Step 12: Leak detection commissioning — simulate leak, verify automatic shut-off response
Coordination with Plafotherm installation (see 04-flooring-ceiling-spec Section 11.2): Water supply pipes must be installed after the ceiling suspension substructure but before the Plafotherm panels are fitted. This slots into steps 1-2 of the Plafotherm sequence (install suspension, route heating pipes) — water pipes are routed in the same phase.
13. Estimated Annual Operating Costs
| Item | Interval | Cost per Change | Annual Cost |
|---|---|---|---|
| Sediment pre-filters (2x) | 3-6 months | 10-20 EUR | 20-80 EUR |
| Carbon pre-filter | 6-12 months | 30-50 EUR | 30-50 EUR |
| RO membranes (2-4) | 2-3 years | 100-200 EUR per membrane | 70-200 EUR |
| Remineralization media | 12-18 months | 30-50 EUR | 25-50 EUR |
| UV lamp | 12 months | 40-80 EUR | 40-80 EUR |
| Electricity (pumps + UV) | Continuous | ~0.5-1.0 kWh/day | 60-120 EUR |
| Reject water (sewage cost) | Continuous | ~100-250 L/day | 30-60 EUR |
| Total | 275-640 EUR/year |
This is the cost of drinking laboratory-grade water from every tap. For context, a family of four spending 50 EUR/month on bottled water would spend 600 EUR/year — with plastic waste and without whole-house coverage.