The need to clean...
Central heating systems can gradually build up a combination of scale, sludge and corrosion by products within the boiler, pipework and radiators. This manifests itself as cold spots on radiators, failure to pump to the furthest radiators, and noise in the boiler. Central heating systems also need to be flushed prior to filling with preservative in order to remove flux and other deposits before commissioning for the first time (BS7593:1992). It can often be time consuming or impractical to remove radiators for cleaning out severe blockages. Even when they are removed, the only flushing capability usually available is with cold water from a hose at mains pressures and flows. This will not loosen or remove sludge which has bonded to the inside of radiators or the remainder of the heating system. The Calmag CalFlush Flushing System is the culmination of many years experience of the use of Calmag Heating System treatment chemicals with high flow, low pressure cleaning sets.

High Flow Flush
Fouled heating systems can be cleaned whilst in normal service with Calmag products which are left in the system to recirculate for a period of a few days. However, this requires multiple visits to the site and often frequent draining down and refilling to restore badly fouled systems. This process can be simplified and shortened by recirculating the cleaning solution at a high flow through the system, while alternating the direction of flow. Thorough cleaning can be completed in a short time with high efficiency and minimal disturbance to the existing heating circuit.

Achieving the best results
Mega Flushing is a mechanical method of combining high flow and low pressure with suitable chemical cleansers in order to cleanse dirty, problematic wet central heating systems. The success of a Mega Flush will be determined by several factors, these factors should be carefully considered before the process begins.

System Design: System design is the main consideration when deciding the type of flush to carry out. When it is not possible to control the direction and flow of water through the system the final results may not meet expectations.

Time taken for the flushing: The time taken to carry out the Mega Flush operation will depend upon the severity of contamination within the system. For a typical system with ten radiators with standard 15mm twin pipe configuration and assuming there are no unforeseen problems, four hours should be sufficient time to complete the job. This time will not be significantly shortened with extra manpower, as this will not reduce the time taken for the machine to clear each radiator.

Procedure followed during flushing: The procedure followed during the Mega Flush will greatly influence the effectiveness of the clean. To ensure best results, it is important to control the path of flow through the system; failure to do this will result in water taking the line of least resistance and an inadequate flush.

Treatment following a Mega Flush: Flushing a dirty or problematic system is only the first step in resolving system problems. During flushing, corrosion debris and other contamination is removed from the surfaces of the system. Failure to adequately protect the reactive surfaces uncovered by the flushing process will result in a repeat of the problem. In certain circumstances, where problems have been severe, it may be wise to use an increased dosage of inhibitor to promote passivation and so ensure optimum protection of system metals.

Systems not suited to Mega Flushing
The effectiveness of the Mega Flush will be determined by the level of control maintained over the flow of water through the system. Poor control of the flow will result in unsatisfactory results. Systems where Mega Flushing will not give satisfactory results are as follows:-

Single Pipe Systems: As a single pipe system relies on hot water displacing cold, the high flow created by a Mega Flush will reduce the flow through the radiators. The flow will also follow the line of least resistance and so in the event of a radiator suffering from a high level of deposits, the flow will pass by without affecting the problem.

Gravity Hot Water Systems: If a Mega Flush is carried out on a system with a gravity hot water circuit, without any method of preventing circulation through the hot water coil, the flush will be ineffective.

Twin Entry Radiator Valves: Systems fitted with twin entry radiator valves should have them upgraded to single entry valves before flushing commences; failure to do this will render the flush ineffective.

Primatic Systems or Thermal Stores: Where a system is connected to a Primatic or Thermal Store cylinder, the cylinder should be isolated and flushed separately using a manual flushing method.

Microbore and Minibore Pipes: As the CalFlush machine is designed to produce high flow but not high pressure, any reduction in pipe size will result in a decreased flow through the system. If the correct procedure is followed when these types of systems are cleaned, the results will exceed those achievable by manual techniques.

Anti-gravity Valve and Built-in Circulators: Although systems with a circulator that cannot be removed, or systems fitted with an Anti-gravity Valve can still be flushed, it is important to flush only in the direction of normal flow.

Primary Checks
Before commencing any flushing work it is important to establish whether the system is sealed or open vented. If the system is open vented, the cold feed and open vent must be capped off. If possible, the system should be operated for a short period prior to work being carried out, in order to identify any major system problems such as cold spots, pumping over, noisy circulator or heat exchanger, or gassing problems.

Maintenance
The Calmag Mega Flush 1 Flushing System has been designed to give a long service life with minimal maintenance. However, a few simple tasks need to be undertaken after every clean or periodically to ensure that the System remains in top condition and continues to deliver outstanding performance.

Post use: Each time the Calmag Mega Flush 1 Flushing System is used it should be thoroughly cleaned to remove deposits flushed out from the heating circuit that have accumulated in the sludge trap at the front of the cleaning solution tank.

Routine: The connection hoses and mains power flex should be periodically examined for signs of abrasion or wear and replaced if necessary.