CENWAT Inhibitor & Water Treatment 2

Question 1

What is a system cleanser (flush chemical) used for?

Accepted Answer

To break down and remove sludge, scale and corrosion products during a power flush or chemical flush

Answer

System cleansers (e.g., Fernox F3 or Sentinel X400) are dosed into the system water to loosen and dissolve sludge, scale and corrosion deposits, which are then removed during a power flush.

Question 2

What is a scale inhibitor and when is it particularly important?

Accepted Answer

A chemical or physical device that reduces limescale formation, particularly important in hard water areas

Answer

Scale inhibitors (e.g., polyphosphate dosers or chemical scale reducers) are used in hard water areas to prevent limescale from forming on heat exchanger surfaces, maintaining efficiency and preventing premature failure.

Question 3

What is the water hardness level above which a scale inhibitor or water softener is typically recommended for a boiler?

Accepted Answer

Above 200 mg/l (as CaCO3) or as specified by the boiler manufacturer

Answer

Most boiler manufacturers and industry guidance (e.g., HHIC, BS 7593) recommend scale protection measures when the water hardness exceeds 200 mg/l (20 Clarke degrees), which is common in south-east England.

Question 4

What standard provides guidance on water treatment in central heating systems?

Accepted Answer

BS 7593

Answer

BS 7593 (Code of practice for treatment of water in domestic hot water central heating systems) provides guidance on flushing, inhibitor dosing, water quality and maintenance of central heating system water.

Question 5

What is antifreeze and when is it used in a central heating system?

Accepted Answer

A glycol-based additive that lowers the freezing point of system water, used in vulnerable systems such as holiday homes or systems with external pipework

Answer

Antifreeze (typically propylene glycol based for heating systems) is added to system water to prevent freezing in vulnerable systems such as holiday cottages, or where external or unheated pipework runs are present.

ACS CENWAT Practice Test

ACS CENWAT Practice Test

CENWAT Inhibitor & Water Treatment 2