Gunge and slime in C/H expansion tank again

[bjh]

Hi. We have a flat roof so the expansion tank is in the airing cupboard. It became rather smelly and on checking found there was some gunge on top and lots of slime build up in the tank. I removed as much as I could and then drained the system down. I flushed it for a couple of hours drained down again and filled up adding system cleaner. Ran the pump for about 3 hours, drained down again, filled up again and then drained again. Then filled up adding inhibitor and anti-kettling. All was fine for 4 weeks. The smell has now returned, but there is no gunge layer on top yet, but I suspect there will be soon.

I don't fancy going through all this again and thought about maybe adding Milton steralising fluid to the expansion tank to kill everything, but not sure if the chemicals might cause problems later. Any ideas please?

 

[lame plumber]

might be time to have a chat with a plumber and look at converting your system to a sealed system, water in a nice warm airing cupboard will always turn horrible over time, luke warm, bit of slime for food and you have a lovely gunge breeding ground.

 

[bjh]

Hi lame plumber. Thanks for your quick response. I'm coming to the same conclusion. I would like to keep the system going a bit longer and was hoping someone out there would know if anything could be added to the tank to kill off what is there without causing any damage. I've worked on big cooling water plants and they all have chemical dosing plants to combat the problem. I would have thought that most open systems would have the same problem and there would be a commercial product available for domestic heating. The smell is now getting worse! I think the crust kept most of the smell in before I cleaned it all out!!!

 

[jtsplumbing]

Had this a few times one of the most common faults is inhibitor just gets poured into the expansion tank and sits there without getting drawn into the system.

 

[Dsp]

Some disinfectant in there shouldn't cause a lot of problems zaflora is my go to product for bad smells

 

[kris]

Hi bjh , i know u said you flushed it a few times , was the tank spotless because its just as easy when the system is drained to shut of the cold supply and disconnect and remove the tank, because its fine and small take it outside and give it a good clean as flushing can sometimes allow any dirt that lies on the bottom of the tank to go down the cold feed when re filling so by removing the tank you can get it spotless and free of stench lol , but what lame suggests isnt expensive to do and can usually be done in a couple hours if everythings accessible,
If you are pouring inhibitors into the tank i usually pour it in as the tank is filling so it gets put through the system properly ,
Is the smell coming from the water lying or are you getting a slight smell from the open vent ,

Have a read of this,

Avoiding Bacterial Contamination

 

[bjh]

Thanks jtsplumbing. I did pour most of the inhibitor in while the system was filling, but the last bit did go in a bit late, so did not go fully down the hole. Not sure what is in the inhibitors, but could this create a smell?

 

[bjh]

Hi Dsp. Thanks for your reply. I was thinking of adding something like Milton but was worried about chemical attack. Disinfectant normally contains chlorine and that just loves eating most things :drool5: especially brass as used in many valves. I will be needing a new boiler hopefully it will last out to the new year, so am tempted to just add something to the tank for now.

 

[bjh]

Hi kris. Many thanks. Had a look at your suggestion and it does look like there is something out there to add to the tank.
This time I did not remove the tank because it is very awkward being at the top of and inside the airing cupboard. I have to remove part of the support framework! Last year I did remove it and thoroughly cleaned it and flushed the system.

The smell was coming from the water, last time I did steralise the water in the tank and then pushed the ball valve down to flood the vent line to steralise all that.

Will now try and get some LP Sterox. Just need to work out volume of water in the system now to make sure I do not overdo it.