Lateral services distribution on site are generally in busy zones with minimal installation space. There are multiple disciplines working with various timeframes and requirements, who each have to have completed their works prior to the next discipline install. If one installation package does not align with a later installation works, alterations to the lateral distribution can snowball, growing in complexity and including compromises on best practice installations.

I would like to share my experience through numerous design reviews and installation inspections, as well as possible suggestions for the design process to reduce the risk of uncoordinated design and installation packages.

Identifying The Disconnect and Complications.

It has been clear that there is a disconnect between consultant’s design intentions and contractor’s on-site installations due to coordination of services. One area of particular concern from a heat network perspective is the setting of lateral distribution network pipework between the vertical risers and HIU terminations.

See below an example of the pipework setting down to a pair of isolation valves, only to then set up into the dwelling.

Pipework setting down to individual dwelling isolation valves then setting up into the dwelling, requiring air vents on dwelling service.

It is altogether too common to see pipework leaving a riser at high level, only to then set immediately down and up again to allow the service to run tight to ceiling. Further settings up and down are often seen on the terminal pipework runs to the HIU within the dwellings, with primary LTHW services often setting around domestic ventilation/high level drainage and water services. At the point of construction, these issues are sometimes unavoidable and should instead be targeted at design stage, with consultants reviewing their network distribution holistically to ensure that the most efficient and cost-effective designs are provided.

Each set-up of a primary LTHW service requires air release valves to remove the risk of airlocks within the system. These air release valves can consist of manual or automatic release valves, with automatic release valves being typically installed where sufficient space is available due to the reduced installation works and access works during the construction of the development.

Leaking Automatic Air Vents can cause significant fabric damage if not caught early.

However, the installation of air valves leads to further complications such as the following:

  • Increased maintenance requirements, with automatic air vents particularly requiring regular inspection to ensure that the product has not developed a leak.
  • Water quality risks, as a result of pockets of stagnant cooler water within automatic air valves or dead-legs of pipework associated with manual air release valves.
  • Building fabric damage, both as a result of leakage of the system, as well as the cumulative effects of regular access to the ceiling system to inspect these products.
  • Additional drain cocks required throughout the network to fully drain such pipework systems.
  • Increased detail within construction and O&M drawings required to identify the location of these systems for future maintenance.
  • Increased difficulty to correctly insulate the full system to CIBSE CP1 compliance, increased network heat losses and associated overheating risks.
Terminal runs requiring air vents as a result of rising pipework from branch network. Connection to the rising branch instead of the lower branch can remove air vent requirements.

Design And Construction Principles to the Rescue!

Yes, we surely can do better and I have a few suggestions on how this can be achieved. FairHeat have pulled together a number of design and construction principles for lateral network distribution to aid designers and contractors on system design to limit these issues, with general recommendations as listed below:

  1. Wherever possible, pipework is to set down from mid-level of the floor above, to high level within the riser.
  2. Pipework is installed with a minimal fall from the riser of c.1:250 where possible to reduce risk of local high spots within the network.
  3. Upon exiting the riser, the pipework should only drop where branch pipework is required to set around LTHW services, and when dropped it should then stay at this lower level, with other services coordinated around the LTHW. In situations where the pipework runs in multiple directions after leaving the riser, it can be beneficial to run a pair of return pipes either side of the flow pipework, with the service combining within the riser. This prevents unnecessary pipework drops reducing already restricted ceiling voids. Additional flow pipework should be avoided where possible due to the increased heat loss of the service.
  4. Where there is a choice between the flow and return pipework setting down, it is recommended that the return pipework sets down, to ensure the flow pipework stays at the highest part of the system.
  5. Where pipework is required to set down, the level of each set should be calculated and clearly marked on layout drawings to ensure services can be fully coordinated.
  6. Where automatic air vents are installed, it is preferable to install commercial grade valves which include large air gaps between the internal valve components and water to reduce risk of leakage.
  7. Where the design/installation of lateral works is undertaken by multiple designers/contractors, a single designer/contractor can be nominated as lead and responsible for ensuring the design/installation is fully coordinated and producing coordinated design/working drawings.
  8. Where manual air vents are installed, these are to comprise of two isolation valves, one of which at the end of the vent in a suitable location to collect any water from the system for close control, and the second to be located as near as practically possible to the pipework tee, to minimise volumes of stagnant water.

I would be very interested to hear other people’s experiences and methodologies for avoiding these issues, any comments/ideas please let me know!