try a few drops of Jeyes Fluid on the surface of water butts. I have three butts I currently use and have no problems.

Our water but is open to the air and never smells, do you have lid on yours?

Does it have a lid? A good fitting lid will solve a lot of problems.

Mine both,have a well fitting lid and a filter .one came with the kit,but the second one didn't ,and we couldn't find one to buy separately..it now has an old tea strainer instead :o) Not sure if it helps really,as we don't get a lot of detritus in it,Never had a problem with smelly water..

Probably sludge in the bottom. Best to empty all the water out and hose out the butt with the hose. It will soon fill up again with fresh rain water.

Bloomer - filters are available from a company called Guttermate - their advertising regular pops up for me on GoY (may be because I looked at their site once when I was trying to find a diverter kit to fit my cast iron downpipe)

Thanks Urbanite.They stopped selling them separately at any of our local garden centres,and we didn't need another full kit pack..I'll take a look,much obliged ..:o)

Hi Bloomer,
I have 4 waterbutts and it is the one I use the least (because it is more difficult to get at) that gives smelly water. I found this out because one of the others used to be left for quite long periods and the water smelled disgusting, but now that I use it a lot the water is without smell. Therefore I have concluded that, in my case, lack of regular use was the cause. I would not have an open water butt having seen several birds drowned in them and in open cattle troughs without an escape route.

I meant to add that to my comment Penny farthing,,about it needing to be used on a regular basis..I totally agree with you on that..We draw some off for other purposes,for that reason,even if we just throw in on the patio and give it a brush,or to rinse the car,after washing..well,not me ,my OH ! :o)