What they said. Just enjoy your hookah the way it was meant to be enjoyed. If you want to fill a scuba tank, you need a proper scuba compressor and a bit of
training. Or take it to a dive shop.
Filling tanks at a dive shop is not that expensive, unless you dive like every day. They will of course expect you to be certified, for very good reasons. You can find videos on youtube of all the skills you will have to learn and demonstrate for
certification. It will be an eye opener, I think. When you are comfortable and confident with actually going through all the drills in the
water, you will be able to meet all the common mishaps that can ruin your day or take your life. Scuba
diving is inherently dangerous and the excellent
safety record that scuba diving has, is due to the
certification process and safety standards.
If you already own a tank, BC, reg, computer, etc, you have already spent over twice what open water certtification costs. Go the extra distance. I didn't, and I had a potentially tragic moment of panic in shallow water in a situation where with snorkel or hookah
gear I would not have had a problem at all. It is different. More things to check. Bouyancy control is a skil that you have to develop to the point where it is automatic, like riding a bike. And I am not even touching the subject of decompression after spending time at depths greater than 20-30 feet. Familiar with Boyle's Law, and its significance to diving? Importance of not holding your breath while ascending? Seriously, if you want to scuba, take the
classes. Then not only can you dive safely, but you can get your tanks filled at any dive shop in the world.
Many dive shops also fill tanks for paintball warriors, who charge their paintball
guns from the tank. Generally those that do, require a sticker on the tank that clearly states "Not For Underwater Use" or something like that. I am only mentioning this because some dive shop operators and clerks might mention it and I want you to be aware that you are taking your life in your hands by doing this, and that while there is no right way of doing this, there are "less wrong" ways. You need to practice all the skills required in the certification process. You can do this with a BC and empty tank, breathing with your hookah hose, if you have a way of adding air into your BC. You will need a couple pounds more weight than with a full tank.
Homebrew compressors have been used, both successfully and unsuccessfully. The unsuccessfully ones can have serious consequences. Don't assume you know what you are doing if you don't. The Max-Air 35 is a popular compressor that sells new for under $3k. A Davy SCU100 is around $2300. There are cheaper options, and you could possibly find a suitable compressor used for around $1k but you would need to have it checked by someone knowledgeable before using or servicing it.
Yes, compressors are expensive. Delivering 3000PSI+ air is complicated. You cannot compress air to 3000PSI in a
single stage. It would be hot enough to melt hoses. SCUBA compressors use multiple stages with intercoolers. They provide air that is free of contaminants like compressor
oil.
Cheap compressors take a long time to fill a tank. Bad air can injure or KILL.
If you dive a LOT, or provide air to more than one or two divers, or are often isolated for long periods of time and need to dive, you want a compressor. Otherwise it makes more sense to fill tanks at a shop. For a small portable system that doesn't consume much
power, stick with hookah diving. For most
liveaboard or cruising yachties it is probably the most practical option.