I used to use supermarket carrier bags inside normal bags, and they lasted fine for a few weeks, but then they started costing 5 pence each which I didn't like. It's now up to ten pence each, and even worse the local farm shop can no longer give them away for free so I can't bypass previous legislation.
If I was cycling daily as I used to, I might consider buying a roll of bin bags from local supermarket as that works out cheaper per bag than what is now extortionate for something that was useful, free, and recyclable.
Depends a lot on what you are using them for. I have one Alpkit drybag I use as a float when wild swimming. It keeps my clothes and towel dry as well as my tracker. I very much doubt a carrier bag would do this...
I use 5l alpkit Airlok extra bags on the blackburn cages on my front fork when I do deep winter stuff and need the extra capacity.
I also tend to use an airlok extra with my duvet jacket in it, on the underside of my aero bars, which can get a lot of spray.
I have a number of the lighter Alpkit airlok bags for splitting my kit up in my tailfin, keeping my kit nice and dry in there.
All of these cases, as you can see a supermarket carrier bag is really not even close to appropriate...
You've probably bought something already, but Ortlieb do a range dry bags. They even do a line with a clicky valve in them so you can properly compress them.
Do ortlieb do really light weight ones tho? Last I looked they only had the really heavy duty ones. I've got a couple, but they are so heavy, I don't use them.
Rubble bags from Screwfix are much stronger and last for ages - my liner of choice for panniers and on-bike bags
I want dry bags that are sufficiently protective that I can drop the bag in the river, and the contents are protected...
This bit I don't know about, but I have a SeaToSummit one that has given me good service, and wasn't very pricey, as I recall.
Sea to Summit I can get here. I shall get a couple to test.
Do you have Sports Direct over there or is it just a UK thing?
Sports direct are a UK only thing AFAIK. I don't think their employment practices would work in any other places.
Another vote for sea to summit. I got a variety pack of sizes a few years back and still going strong.
I'll give them a go.
I use the Osprey ones, mostly because they were often on sale on Wiggle.
They are very light and I find between the 3L and 6L cover most bases and I have them in different colors.
I have also in the past put a bit of folded masking tape over the tab they have on one end to make a label which I have then written handy descriptions such as North and South for when I've used them in drop bags on LEL etc.
Bever.nl sell those, shall get a couple to test.
Mine is EXPED, my wife bought a multipack of different colours from Cotswold Outdoors some years back. I use the small orange one for phone and card wallet when on the bike. It sits in the centre back pocket of a cycling jersey. Have used the larger ones inside a saddle bag or even strapped to the top (there's a yellow one that works well for that). Really useful bits of kit. After regular use the inner lining starts to break up but that takes a while.
ooh, Exped are easy to find here, shall get some to test.
decathlon has some lightweight ones in their canoeing aisle, but only in bright orange iirc.
I have one bright orange, for swimming, else I really like muted.
I have several of these in various sizes. Also the guilt about having bought from Sports Direct.
The bags are rated for touring in Wet Wales and are more robust than the thinner Alpkit ones, so good if you're intending to use them outside of any containing bags. Not exactly muted colours though.
If you're struggling to find what you want, dry bags aren't so hard to make. If you've access to a sewing machine and some patience you could cost up a shopping basket of bits from https://www.extremtextil.de . Silnet or similar to seal the seams.
I don't have the means to tape the seams. Home made dry bags aren't going to be very dry. I don't think I would trust them.
But thanks for the reminder about extrem textil, I have some other kit I want to try to make.
J