WATER TREATMENT
Water treatment and conditioning in commercial heating systems
With the forthcoming Heat Network Technical Assurance Scheme (HNTAS) regulations and existing Building Regulations Part L, Steve McConnel, director, Industrial and Commercial Heating Equipment Association (ICOM) and Manufacturers of Equipment for Heat Networks Association (MEHNA) explains how commercial building owners and contractors must adopt best practices in water treatment to comply with legal requirements, ensure optimal system operation, and reduce environmental impact
E
nsuring that water quality is properly managed in commercial heating systems is critical to maintaining energy efficiency, system longevity, and reliability. Whether heating systems are standalone or part of a heat network, proper water treatment and conditioning help prevent costly failures and inefficiencies. Neglecting water treatment can lead to corrosion, limescale buildup, sludge formation, and biofouling, each of which can compromise performance, increase energy costs, and lead to system breakdowns. Water treatment is crucial for preventing common issues in commercial heating systems. The combination of water impurities, heat, different metals, and the introduction of dissolved oxygen can lead to the following major problems.
Corrosion
Corrosion occurs when metals degrade due to reactions with water and oxygen. In untreated systems, this can lead to pipework deterioration, pump failures, and leaks. Mild steel, iron, and aluminium components are particularly vulnerable. Aluminium, often used in high- efficiency heat exchangers, requires careful pH management to maintain its protective oxide layer. Failure to do so can result in rapid corrosion, compromising system performance.
Limescale
When water is heated, calcium and magnesium salts precipitate and form limescale deposits. Hard water affects over 60% of England, making limescale a significant issue for commercial buildings, especially in the South, East, and Midlands. Limescale reduces heat transfer efficiency, restricts water flow, and increases energy consumption. British Water estimates that just 1.6mm of scale can reduce heating efficiency by 12%, while 6mm can lead to a staggering 40% increase in energy bills.
Sludge
Sludge is formed from a mix of corrosion products, including iron oxide and magnetite, which accumulate in the system. This can lead to blocked pipes, inefficient heat transfer, and increased energy usage. Pumps, valves, and
radiators are particularly vulnerable, with ‘cold spots’ in radiators often indicating the presence of sludge.
Biofouling
Biofouling occurs when bacteria and microorganisms build up within a heating system, forming biofilms on pipe surfaces. This can not only reduce efficiency but also pose serious health risks, particularly if Legionella bacteria are present. A biofilm as thin as 20 microns can cause up to a 30% decrease in thermal efficiency within heat exchangers, making biofouling a hidden but costly problem.
Treatment and monitoring
Effective water treatment for commercial heating systems involves a multi-faceted approach.
1. Pre-treatment of fill water
The quality of supply water at the commissioning stage is critical. Water should be tested and, if necessary, treated before being introduced into the system. This can involve filtration, softening, or demineralisation to remove impurities that contribute to scaling and corrosion.
2. Chemical water treatment Adding appropriate chemicals helps control corrosion, scale, and microbial growth. Building Regulations Part L states that:
“Central heating systems should be thoroughly cleaned and flushed out before installing a new boiler.”
“A chemical water treatment formulation should be added to the primary circuit to control corrosion and the formation of scale and sludge.” Corrosion inhibitors, biocides, and scale
preventatives play a crucial role in maintaining system integrity.
3. pH management The correct pH balance is crucial to preventing corrosion, especially in systems containing aluminium. pH buffers help maintain the ideal range, preventing both acidic and alkaline damage.
4. Solids removal and filtration Dissolved and suspended solids must be removed to prevent blockages. This is achieved through physical filtration systems, such as
magnetic filters, which capture magnetite sludge before it causes damage.
5. Galvanic anode cathodic protection This electrochemical method helps protect metal components from corrosion, particularly in mixed-metal systems.
6. Bacteria and biofouling inhibition Adding biocides and bio-dispersants controls bacterial growth, preventing the formation of biofilms that reduce efficiency and pose health risks.
7. Ongoing monitoring Regular testing ensures that water treatment remains effective. Testing should measure: • Corrosion inhibitors (e.g., Molybdate, Sodium Nitrite)
• Dissolved metals (Iron, Copper, Aluminium, Zinc)
• pH levels • Chloride and conductivity • Suspended and dissolved solids • Data from over 6,000 commercial system tests* shows that 45% failed for Molybdate levels and 44% failed for Sodium Nitrite levels, highlighting the need for better monitoring and adherence to standards such as BSRIA BG50/2021.
HNTAS: a positive step for heat networks
The forthcoming Heat Network Technical Assurance Scheme (HNTAS), launching in 2025,
10 BUILDING SERVICES & ENVIRONMENTAL ENGINEER APRIL 2025 Read the latest at:
www.bsee.co.uk
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42
