The Systems

Water System

Specification notes:

  1. Water systems to comply with Good / Best Practice aspects of AECB Water Standards and the accompanying Technical Guide. Notably:
    1. Insulation on both hot and cold pipes (Armacell Class 0 Armaflex ?)
    2. Separate sub-meter on hot water system
      1. Really want to monitor Heat rather than just water volume, so use a heat meter instead
      2. As with other  heat meters, follow the RHI recommendations (EU Measuring Instruments Directive (MID), EN 1434). Class 2 is more accurate than Class 3
      3. All meters to be connected via an M-Bus interface
  2. Appliances should ideally be on the Water Technology List
  3. Need to review target flow rates for taps and showers – since there is no mains drainage and water heating will be carbon-efficient the benefit from reducing water consumption to an absolute minimum is limited
    1. Aim for 5l/min for basin taps?
    2. Aim for 9l/min for shower heads?
  4. Low flow taps should be supplied by small bore pipes
    1. Details of pipe volumes and flow rates here
  5. Consider secondary circulation for domestic hot water, to reduce “dead leg” effects?  No: best to avoid the need for that, because of heat loss and pumping costs. Small bore pipes and sensible routing should help a lot.
  6. Since the Severn Trent meter is so far from the house, add a second meter where the supply enters the property in order to detect small leaks on the supply pipe
    1. An internal meter is also required for compliance with the AECB Water Standards
    2. Best to use a Rotary Piston type, for increased accuracy (especially at low flow rates)
    3. Something like the Itron Aquadis, with an M-Bus interface (Cyble)
  7. What about big leaks? Would an (automatically monitored) pressure gauge on the supply pipe detect those? Alternative leak-detection solution?

Rainwater Harvesting System

Specification notes:

  1. BS8515:2009 applies
  2. Need a pumped system in order to feed bathroom on 3rd floor, since there’s nowhere higher to locate a header tank which needs to be around 1.2m above the highest appliance.
    1. Also, header tanks can have issues because they store water at higher temperatures than the underground tank and hence might require something like the RainDirector
    2. Would a header tank system provide enough pressure for a garden hose? Probably not, whereas a fully-pumped system will be fine
    3. It’s a good idea to include an accumulator (expansion vessel) so that the pump doesn’t need to fire up to pump 4 litres every time someone flushes a toilet
  3. Use for all toilets, outdoor taps and washing machine
    1. Washing machine will probably benefit from an extra filter – something like this (also at Wickes, slightly cheaper)
    2. That filter is clearly branded “grünbeck” but is not currently listed on their website. Maybe something like this as an alternative
    3. Might as well have the filter process all of the water, not just for the washing machine – or would that cause other issues?
  4. For filtering the incoming water, the WISY Vortex Fine Filter looks like the best option available, especially since it needs little maintenance or cleaning
  5. Locate the tank(s) under the courtyard between the house and the outbuildings? Should make for shorter pipe runs, and there should be plenty of space there, and no risk of needing to dig in that area for other purposes
  6. Metered to record usage; separate meter for outdoor taps?; separate meter for mains top-up?
  7. Outdoor taps at various locations throughout the garden?
  8. Measurement and recording of level / volume held in storage tank
  9. Average annual rainfall for the area (1981-2010) is 620mm.  The total (plan) roof area is roughly 162 m^s (house) and roughly 282 m^2 (outbuildings) giving a total of roughly 444m^2. Based on the guidelines from UKRHA assume the filter is 90% efficient and another 10% is lost to evaporation so that gives 620 x 444 x 0.9 x 0.9 = 223,000 litres. Actually the WISY VFF is more like 95% efficient so say 235,000 litres.
    1. UKRHA say to size the tank at 5% of that, in other words 11,750 litres
    2. Other sources say to allow for more usage on a large garden – more like 15,000 litres?
    3. Looking at Usage rather than Collection, that would indicate going smaller rather than larger – something like 6,000 litres
  10. The overflow presumably needs to go via an Attenuation System, to reduce the peak outflow to the watercourse in the event that the Rainwater Tank is full when a bad rainstorm occurs.
    1. Something like this?
    2. Actually a variable-level “balancing pond” as used in a lot of commercial developments is probably a better idea.

Settled on using a system from consisting of:

  • A 6,000 litre RainSava GRP storage tank (data sheet)
  • A Wisy WFF150 vortex filter
  • A Multigo 40/06 submersible pump

Also need an expansion vessel on the pressure side to reduce cycling of the pump. Since the main usage of the rainwater is for toilet flushing, and since the toilets are specified to be 6 / 4 litre dual flush, it makes sense to only fire the pump every few flushes. Something like a 24 litre expansion vessel should help a lot – see e.g. this one.

TODO: Decide on the pump controller.

Heating System

  1. Building to (near) PassivHaus standards means little space heating is required
  2. Still need lots of domestic hot water though, and some sort of top-up space heating for the winter
  3. Thermal store to supply DHW and limited heating (underfloor and towel rails in bathrooms)
    1. Akvatherm?
  4. Hybrid PV-T Solar PV / Solar Thermal panels coupled with a heat pump looks like a good way to go
    1. See (in Administration as of January 2015; URL returns “Server Not Found”)
    2. Can choose between two styles of panel to favour PV or Thermal output
    3. Suitability for DHW in dull winter weather???
  5. Still need some sort of emergency back up heating though – especially since the electricity supply is via overhead poles
    1. Small log-burning stove?
  6. Alternatively, could go with a small log-fired boiler
    1. Something like the Atmos DC 18S (£1300 GBP inc VAT from
      1. That doesn’t seem to be exempt from the Clean Air Act though.
      2. The Fröling S4 Turbo (15kW upwards) is exempt, as is the Angus Super 18.
  7. High efficiency circulating pumps
    1. Grundfos Alpha2 ?

Electricity Supply Considerations

  1. The electricity supply is via overhead poles, previously a single phase (240V) supply fed from a pole-mounted transformer in the direction of Thulston Fields Farm.
    1. This is likely to be more subject to failure in bad weather than an underground supply. As a result it would be good to have some element of standby generation, at least for critical services.
    2. It would also be advisable to install surge protection to prevent damage to sensitive electrical devices in the event of a lightning strike or other over-voltage event.
      1. In the UK it seems more common to have surge protection in 4-way adaptors or in individual plug-in adaptors rather than a device installed in the consumer unit to protect the whole installation. Perhaps that’s because overhead supplies are the exception rather than the norm.
      2. See here for some guidance notes from Schneider Electric.
      3. See also
  2. Assuming some sort of Solar PV installation for on-site micro-generation, note that the limit for Small-Scale Embedded Generation (SSEG) is 16A per phase. See the documentation for G83 for further details. (16A on single phase @ 240V is 3.84kW.) 4kW is the cut-off for the highest level of Feed In Tariff payments, with 10kW being the cut-off for the next highest level.
  3. Any special considerations for high-speed recharging of electric vehicles? 32A / 7kW connection required?

Electrical Outlets

  1. Individual RCDs for appliances containing water heating elements, so the local RCD trips (rather than the circuit RCD) if the heating element fails with an earth fault
    • Washing machine, Dishwasher. Coffee Maker, Kettle?
  2. Shaver sockets suitable for electric toothbrushes in bathrooms, one per sink
  3. Wiring and flex outlets for mirror heaters in Master Bedroom and Guest Suite En-Suites, one per sink
    • Controls for these based on temperature and humidity?

Sewage Treatment System

Specification notes:

  1. Existing property used an old Septic Tank, still in-situ as of 2013-01
  2. Previous planning permission shows the old tank replaced with a Biodisc-style treatment plan discharging to reed beds
  3. Environment Agency seem fairly relaxed about small-scale sewage treatment plans unless they are in “Source Protection Zone 1”
  4. Marsh Flatts Farm, along with the surrounding area, is in a “Safeguard Zone” for “Drinking Water Protected Area” GB104028053240 (River Derwent from Bottle Brook to R Trent)
  5. New sewage treatment plant systems need to be certified to BS EN12556-3:2005. See the British Water list for certified systems.
  6. An unpowered system such as the Conder ECO warrants further investigation.
  7. There’s another unpowered, naturally-ventilated system called the BIOROCK that looks like the best option. Get the best results with two, separate Primary tanks upstream of the Treatment tank; 3 tanks in all. Note that the outlet is relatively low in the tank and needs to be pumped to a higher level on flat ground but can drain naturally on sloping ground (which might influence where it should be located).

Settled on using the Biorock system: a Biorock-10 treatment unit with a 3300-litre, 2-compartment primary tank (slightly bigger than the one shown at that link) and a 400mm pump shaft on the outlet, not actually for a pump but mainly as insurance just in case a pump is required in the future.

Gate Automation System

  1. Automated openers on both the Outer (Aston Lane) and Inner vehicle gates
    • The outer gate is the more demanding installation of the two, being the main security barrier, being more isolated and being more subject to damage by vehicles turning in the gateway
    • However, might as well put the same system on both gates (unless there’s a big cost differential)
  2. The gates are nominally 12′ wide (3.66m) and are likely to weigh less than 60kg each
    • This one is listed at 35kg, but something with stronger tubing and ideally also some diagonal bracing would be better, but a bit heavier (especially for when people climb / sit on the gate)
    • Best to go with a standard-sized gate for ease of replacement in case of damage; also cheaper than a custom size
    • OK to go a bit wider but not narrower, to retain access for farm machinery – maybe go up to 13′ (3.965m)
  3. Most automated gate openers seem to be rated for narrower but heavier gates
    • In particular, a lot of the smaller systems are rated for “up to 3.5m”
    • One concern for gate openers is wind loading, but a bar gate will get much less wind load than a solid-panel gate, so maybe
  4. A safe bet would be the CAME Frog Plus (FROG-PM4) which is rated for gates up to 5.5m (though it’s not cheap)

Metering System

Specification notes:

  1. All sub-meters (water, electricity, heat) shall have M-Bus interfaces
  2. Options for integration of M-Bus into the wider system landscape include:
    1. The HWg-PWR (see e.g. the Sensormetrix website here) which is available in 3-, 12- and 24-way variants
    2. The M-Bus to KNX gateway from arcus-eds, website here, which is only available as a 3-way variant but it’s half the price of the 3-way HWg-PWR

Sprinkler System

  1. Consider a fire suppression sprinkler system
  2. BS9251 applies
  3. See BRE report here
  4. Water supply adequate?

CC BY-SA 4.0 The Systems by Marsh Flatts Farm Self Build Diary is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

2 thoughts on “The Systems

  1. There is another UK made non-electric sewage plant called a Filterpod that is worth a look. You don’t need the 5 metre high vent pipes sticking up either as it can be solar powered if required.

    • Thanks for the info John. From a quick scan of their website it looks broadly similar to the Biorock system, but as you say it can have an electric blower which can be solar-powered if required.
      Looks like they only do a 6 PE system at the moment and I need more capacity than that, and I’m not sure I want to be a guinea pig for their larger system when it becomes available.

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