Vaillant ecotec pro 28 major service and repair

This Vaillant repair job was for a customer in Rotherham which I did last week. The boiler was an old ecotec pro 28 which needed needed a service and needed the flexible rubber flow and return pipes replacing. The boiler had not been serviced in its 10 year life.

I do enjoy these sort of jobs where you can take a beaten up older boiler and get it back to working as it should. The customer requested that I replace the flexible flow and return pipe and the G10 burner door seal etc. This boiler was in a slightly worse state than the customer realised and did need a few extra parts other than the parts mentioned.

The customer was extremely pleased with what I did and was kind enough to leave some great feedback on my reviews page.

Upon first inspection I could see that the rubber tubes had shown signs of leaking in the past and probably needed replacement. However I also noticed the diverter valve was stuck and did not move at all. The customer confirmed that the hot water hadn’t been getting quite as hot as it used to.

Reason being was that the valve was stuck almost mid position so a lot of the heat intended to go to the hot water would have been going down the flow pipe into the central heating circuit.

I tried a new diverter valve motor but as I suspected the new motor still didn’t fix the problem as the printed circuit board had failed. I come across this every so often on an ecotec. If the diverter valve motor gets wet or stuck for a long period it can damage part on the printed circuit board that sends power to it.

The board was still working ok aside from not sending enough power to the diverter valve motor. So it was a shame but the printed circuit board needed to be replaced as well. When they fail like this you can usually hear the motor making a very small amount of noise but refuses to move.

Vaillant ecotec failed leaking diverter valve

The diverter valve definitely needed replacement as you could see signs that it had been leaking previously and it started leaking as soon as I move the pin.

So in the end I recharged the expansion vessel which was completely flat. Replaced the internal rubber flow and return pipes, printed circuit board, diverter valve and G10 burner door gasket after cleaning the heat exchanger. I also cleaned the magnetic system filter.

Vaillant ecotec pro 28 Giannoni heat exchanger after 10 years of use

The heat exchanger was surprisingly clean given that it had not been cleaned for over 10 years. I also tested the pressure sensor that was currently fitted and decided it did not need to be replaced.

Silicone grease on Vaillant diverter valve pin

The above image is not the best and its difficult to see, but I usually add a bit of silicone grease to the diverter valve pin which helps to keep to moving freely. I tend do this both on replacement diverter valves and old ones when I serviced them.

Vaillant ecotec upgraded internal copper flow and return pipes

The original ecotec manufactured from 2005 had issues with the internal rubber flow and return pipes. These were upgraded on later models and you can purchase the upgraded copper pipes for the older models that didn’t have them originally.

The flow and return are sold individually and are not the cheapest of components as they will set you back around £100 for the two. Poor maintenance often leads to the tubes failing and leaking.

When the expansion vessel for example goes flat over time as they do, it puts a lot of extra strain on the boiler as the pressure rises a lot higher when the heating is used. This can contribute to the tubes leaking, splitting and in worst cases basically exploding under pressure.

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Areas where I can repair your Vaillant ecotec pro combi boiler

areas that are covered

I cover a large part of South Yorkshire including most of Sheffield, Rotherham and Barnsley. I also cover a small part of Doncaster.


I cover most of Sheffield including central Sheffield, Chapeltown, Ecclesfield, Grenoside, High Green, Oughtibridge, Thurgoland, Wortley, Aston, Aughton, Swallownest, Todwick, Hillsborough and Stannington.


I cover the whole area of Rotherham including central Rotherham, Brinsworth, Catcliffe, Canklow, Masbrough, Treeton, Whiston, Greasbrough, Kimberworth, Thorpe Hesley, Rawmarsh, Wentworth, Bolton-on-Dearne, Goldthorpe, Thurnscoe, Wath-on-Dearne, Mexborough, Swinton, Kilnhurst, Hooton Roberts, Ravenfield, Thrybergh, Bramley, Hellaby, Maltby, Thurcroft, Wickersley and Braithwell.


I cover most of Barnsley including central Barnsley, Birdwell, Stairfoot, Worsborough, Kendray, Ardsley, Athersley, Monk Bretton, Lundwood, Royston, Brierley, Cudworth, Cortonwood, Great Houghton, Shafton, South Hiendley, Brampton, Darfield, Wombwell, Hemingfield, Elsecar, Hoyland, Jump, Barugh Green, Cawthorne, Darton, Dodworth, Gawber, Mapplewell, Pogmoor, Staincross, Wilthorpe, Worsbrough, Thurnscoe and Tankersley.


I cover a small part of Doncaster including central Adwick, Conisborough, Edlington, Warmsworth and Mexborough.