EndoTherm – Additive for Central Heating Systems


How it works:

endotherm-biothermAs hot water travels through radiators and returns to the boiler, part of it contacts with the hot metal of the fired boiler tubes. This boils and transfers heat into the remaining bulk water causing the overall temperature of the system to increase:

At the hot boiler tube, nucleated boiling occurs. Vapour forms within small micro-cracks and escapes as large, irregular oval bubbles. These large bubbles are lethargic and flow inefficiently restricting and obstructing the heat transfer into the bulk liquid and around the heating system.

EndoTherm creates a change in the bulk water surface tension, thereby changing the behaviour of the vapour bubbles emerging from the micro-cracks. In effect, it creates more, smaller shaped bubbles making them less obstructive (with a greater surface area) and able to move more efficiently.


This difference in bubble formation between untreated and EndoTherm dosed systems can be seen in the image bellow.:


This process means the bulk water within a heating system exhibits a greater overall heat transfer coefficient.



  • EndoTherm is an energy saving additive for central heating systems.
  • The effects of EndoTherm have been independently tested and proven by an ISO17025 accredited test house.
  • EndoTherm is proven to be non-corrosive and causes no damage to heating system components.
  • Easy installation in 10-15 minutes.
  • EndoTherm will work in any closed, wet central heating system.


How much EndoTherm do I need?
Domestically 500ml per 100 litres of heating system volume. Simply put a 10-12 single radiator home requires 500ml.
Commercially 1 litre per 100 litres of system volume. Experts from Endo Enterprises can calculate exactly how much EndoTherm will be required.


Does EndoTherm work in any heating system?
Yes, any heating system where a boiler is used to heat water EndoTherm will work.


How long does EndoTherm last?
EndoTherm will remain in a closed central heating system without any deterioration of energy savings for at least 3 years, according to independent tests.


How do I install EndoTherm?
EndoTherm can be added to a system using a feed and expansion tank or via a partially drained radiator. Full installation instructions are available on request.


Does EndoTherm damage my heating qeuipment?
Extensive testing has been carried out and EndoTherm has been proven to have no corrosive or damaging effects on the materials found within heating systems.


Is EndoTherm dangerous?
EndoTherm is not dangerous to the touch. It has been classified as a mild irritant but carries no hazardous threat.


Should EndoTherm be applied to a clean or existing filled system?
EndoTherm will work in any existing system whether “clean” or “dirty”. It is recommended that systems are flushed before the installation of EndoTherm to maximise energy savings.


Can EndoTherm work in conjunction with an inhibitor?
EndoTherm compliments inhibitor products. This applies to systems already dosed with an inhibitor and systems where an inhibitor is introduced after EndoTherm has been installed. EndoTherm has some inhibitor properties itself and functions alongside inhibitors without issue.