I have a G.Worm 100e compact (unfortunately) & although I have heating, whenever we draw water from the hot tap, the boiler does not switch to heat the domestic supply. We are in a very hard water region (Spetisbury, Dorset) and, although I have an electronic water softener, plus a Limemaster immediately before the cold feed to the boiler, I fear that the heat exchanger may be scaled up, restricting the flow speed as we draw off from the hot tap & the draw isn't enough to trigger it. It had got progressively worse over the last 2 years, although it was new 28/01/2002. Or could it be just a lump of scale in the pipe?
Any suggestions please, apart from taking a heavy hammer to it, (this is a replacement boiler from glow worm, our second one, I want a worcester next time) They have driven me crazyover the last 11 years, never again)
Sorry about the rant...
chris wiles

Chris Wiles, May 2005

I have a ideal combi boiler the hot water is not working if I leave my boiler switched on so I turn it off and switch it on when I need hot water it then works. does anybody knows why it is happening.it is 8 years old

ann, April 2015

Water coming out from mechanism beside the pump

Karl, December 2013

Yes look like hot water heat exchanger is scale up need clean up,take out clean with sprit of salt

ltd, March 2012

I have tried reset some times get hot water through taps but when I try the shower it goes cold

eric, February 2012

Our Glowworm Combi boiler stopped heating water. We had a Plumber service it for £70 and another visit to no avail. he had put WD40 on the fan bearing on his 1st visit. I checked the fault finding guide and there was 118V to the fan but it wasn't running ! Took it out and could hardly turn the impeller by hand ! A guy on Ebay sells bearing kits for around £8 (http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=200665057953) I rebuilt the fan using this and prest ! Works once again !
Try this first ? Its easy and safe !

Roberta Jane Upton, October 2011

I have a combi boiler but it is not heating up my water. It first started running cold for a short while then running hot, but now the only way I can get hot water is by putting my heating on too, which is maing it expensive when I do not need heating on.

christine Saunby, February 2011

i have a compact 100e combination boiler i have heating all threw the house but no hot water coming out of the taps upstairs and down stairs could any one help

shawn, November 2009

This boiler would solve most problems in hard water areas because it has no plate heat exchanger and has 22mm water ways on the main heat exchanger Intergas HRE36/30 combi. sold at
http://www.ukplumbingsupplies.co.uk/productdetails.php?productid=723&categoryid=79

chris, October 2009

I had a similar problem. 2 different plumbers changed different parts, ncluding the heat exchanger and it only temporarily solved the problem. I eventually had to work it out myself. It w the diaphram that pushes the switch to turn the hot water on. The diaphram only costs a few pounds. As long as you can get teh screws out then it's an easy fix to do yourself.
If you undo the front panel you will see 2 brass circular fittings. It's the one n the right handside. 4 screws hold it in place. Drain the boiler first. easiest way to do this is to turn of your water supply and turn the overflow tap. Then simply undo the screws and replace the diaphram.
This worked for me after months of trying to find a solution

Steve, October 2008

Hi Chris,

Hope I can help a bit. I have a Worcester Bosch which works on a similar principle to your Glow Worm. Being in a hard water area myself, I have had no limescale problems in the heat exchanger after 7 years, this being without any anti-scale gadgets, so I wouldn't think this is your problem either after only 2 years. In any case, there should be little build-up as the temp should never go above 65 C.
It will either be a problem with your diverter valve or the pressure sensing device/switch. Most boilers also have a gauze filter fitted before the exchanger, and there could well be bits in that. not necessarily scale, but if you've had any work done in your street, eg. water board changing old cast mains to plastic, there could very well be bits of plastic "saw dust" clogging you up.
If you turn on all your hot taps and the flow seems reasonable, then it's probably the boiler divert/sensing mechanism.

Tony, May 2005