It’s a long story which I won’t trouble you with. Save to say that after years of running without a backpack, I was persuaded, and I’m so grateful for that advice.
Mine is not the expensive one recommended by friends at the running club, but a cheap Aonijie one with many pockets. Instead of the old bum bag, carrying two small water pouches, I now have 1.5 litres of fresh water in a system designed for runners.
Over time I learnt that the bladders leak, even the leak proof ones leak! The original slider mechanism was also a pain. When choosing a replacement I prefer the type with a large screw-on cap, and a small screw fitting to hold the union, like the one on the right in the picture below. The one on the left has a larger push fit union with a release button. The push fit union allows air to slowly seep in over time. It’s also more unwieldy when you’re trying to expel all the air from the bladder by holding the union uppermost and sucking the air out through the pipe. The smaller the union, the more you can see what you’re doing. That helps!
In the photo, the old one has gaffer tape covering a (bicycle) puncture repair patch, and that was a temporary repair pending the arrival of a new order. The gaffer tape stops the friction of the fabric backpack from renewing the same hole, allowing the repair to last for quite a while.
On 10k races and half marathons I’m now self sufficient and no longer need to stop at the water stations. The Geneva Marathon saw me follow a twofold strategy, which worked out well, using my own supply and calling at the water stations. What changed before I did the Chelmsford Marathon was the need for energy gel. Having shunned it in the past, I was reformed, and I now needed more pockets and larger pockets to carry gel sachets.
The full story is give in my book The Third Marathon. It explains how I didn’t leave myself enough time to buy, and try out, new backpacks, so I modified my own. By sewing some fabric pencil cases onto it! I needed to carry 16 gel sachets at 60g each. The big pencil cases were partially folded and sewn down, leaving just enough space for eight sachets in each. Then they were attached to the straps in five places (not the obvious six) because I still needed access to the pockets beneath.
I tried it out a few times before my third marathon. I does the job. It may look a bit weird, but it cost me nothing, because I had spare pencil cases at home. A bit of trial and error was involved. Unpicking bits and sewing them again. One connection was too tight to allow a zip to move freely. Another connection was too tight to get my iPhone into and out of the correct pocket. I added some velcro loops (cable ties for computer stuff) which now guide the water pipe, and hey voila! Heath Robinson would be proud!