Buying a compressor to save money

[100days-a-year]

Starting with a new diesel powered compressor and a new large filter tower. Less than $5 per nitrox fill with 1000 fills per year included 02, filters and fuel and assuming I just threw it away after 4 years instead of rebuilding @ 1/4 the cost of new.

 

[rob.mwpropane]

Starting with a new diesel powered compressor and a new large filter tower. Less than $5 per nitrox fill with 1000 fills per year included 02, filters and fuel and assuming I just threw it away after 4 years instead of rebuilding @ 1/4 the cost of new.

Why throw it away?

 

[Tracy]

I tried browsing a few threads before posting, seeing a lot of questions based around "are you doing this to save money?" But there's no real substance as to why this is a common question. I dive 3-4 times per week, and getting a fill at $10+tax is costing close to $250/mo. I'm considering a compressor to save money on fills. What's the logic behind the concern about trying to save money?

It is mentioned because people buy them thinking they will save money. For one diver, it isn't something that will happen. To fill tanks economically, it takes a good sized machine making a fair volume of gas to spread the costs over many many fills. A machine of suitable size for a home user will be crap, nobody builds a good quality long term small compressor. They are essentially disposable machines. Even with regular use, the cost per fill will be more than $25.
Compressors are incredibly handy, I have many of them, but unless you are doing a large volume of gas, you will never save money with one.

 

[100days-a-year]

Why throw it away?

That was for illustration.
The math is pretty simple even on electric ones because the price per kw/h is pretty easy to find.
I burned .4 gph on my diesel engine.
On average 4 tanks per hour. 250 hours per year
Filters, lube changes and other consumables $1k per year max
02 was under $60 a T and we would run it down to under 100 psi
Compressor engine and filter tower were around $12k
This is a common price amongst at least a dozen friends with compressors, both commercial and recreational divers.

 

[broncobowsher]

Why throw it away?

He is speaking the economics of having a compressor. If you consider that it has zero value after 4 years, that is where the numbers play out at. But since it has value, the cost per fill is even lower.

Think of the compressor as a scuba tank. There is an up front cost. After a number of years there is a value if you sell it. What is that value? Depends. A sought after steel tank that has a week old hydro is worth nearly what it was when new. You took care of it, invested money into it getting a hydro, etc. But you are not going to sell it, so how does that actaully play into the economics? On the other hand if you bought a tank, didn't take care of it, now out of hydro and won't pass a visual anymore, you throw it away.
Which of those can you count the cost per use? The one you throw away at the end. There is a fixed cost, a number of uses, and the known maintence during that time. So that is where there is a throw away value.
But if you didn't throw it away, but you didn't sell it either, and you keep using it. How do you figure the costs? You can't. So take worst case, throw it away, and those are the numbers presented. But knowing that there is still value in a working (rebuilt for a quarter the price of new) the ongoing cost per fill is less than worst case.

If you really wanted to you could figure the cost per fill for the first life of the compressor, that is the $5 per fill mentioned. Now you are on the second life of the compressor, but this time instead of figuring the purchase price of a brand new compressor you are looking at the rebuild costs of the used compressor. There will still filter, fuel, maintenance costs that will be about the same as the first life of the compressor (market prices will change slightly) so the second life will be a much lower cost per fill.

So how can you really determine the lifetime cost per fill if the compressor still has life in it? You can't. You can only figure it after the compressor is thrown away. So for the first life of the compressor, before the rebuild, there is a fixed set of numbers. The only way for them to work is to assume the value at the end of the first life is zero.

 

[Gone for diving]

I built my own compressor, and I know it has saved me money, but I have access to equipment and hydraulics, etc,
So just in price of parts first year of pumping for me and my buddy, payed for the parts, and that's not counting driving and wasted time to get the tanks filled,

It's how much you pay for the compressor and how much you can do yourself,

It especially saves money when diving doubles, its twice the price to fill,
and you get to top them off when ever you want,
I can't imagine diving doubles and wondering it you should get it filled, or dive with them 2/3 full, because you did a quick small dive with someone..

8-10$ a fill, 8 × 2tanks= 16$ x 50 dives a year = 800$ that's roughly for me, then a buddy or 2, its definitely worth it for me, plus I get to fill all my vintage tanks that nobody wants to fill,

 

[Ulfhedinn]

Not having to deal with a dive shop is priceless.

I love my shop... but its 90mins away.

 

[bakodiver391]

Buying a compressor to save money is like fu**ing for virginity.

 

[Wibble]

There's considerable savings in cylinder testing and cleaning. Seems that one collects a large number of cylinders which become very expensive if getting them commercially tested and cleaned.

 

[rob.mwpropane]

That was for illustration.
The math is pretty simple even on electric ones because the price per kw/h is pretty easy to find.
I burned .4 gph on my diesel engine.
On average 4 tanks per hour. 250 hours per year
Filters, lube changes and other consumables $1k per year max
02 was under $60 a T and we would run it down to under 100 psi
Compressor engine and filter tower were around $12k
This is a common price amongst at least a dozen friends with compressors, both commercial and recreational divers.

I have to grease the compressor, change the diesel engine oil, and fill it with fuel. Now here's where I have a small advantage to some, we run a small welding shop, and also sell fuel. I have an abiundance of O2 and diesel fuel at my disposal. At some point I'm sure I'll buy a T of O2, but it's $25-$30 from our supplier (that may have gone up due to recent events, not sure what it is right now), and so far I haven't needed to buy one (given I don't dive that much nitrox though). We own 5 or 6 large O2 bottles. The grease I have to use for the Rix I'm sure will last a lifetime.

It is mentioned because people buy them thinking they will save money. For one diver, it isn't something that will happen. To fill tanks economically, it takes a good sized machine making a fair volume of gas to spread the costs over many many fills. A machine of suitable size for a home user will be crap, nobody builds a good quality long term small compressor. They are essentially disposable machines. Even with regular use, the cost per fill will be more than $25.
Compressors are incredibly handy, I have many of them, but unless you are doing a large volume of gas, you will never save money with one.

What about a Rix SA-6? Pumps ~ average 5cfm, doesn't use oil.... still crap in your opinion? Honest question, you know worlds more than I'll probably ever know.

Buying a compressor to save money is like fu**ing for virginity.

Maybe....but that doesn't stop me from trying and it sure has been fun along the way.


Another thought I had was VIP's on tanks. I still get mine hydro'd, and I will still pull them apart to peak inside, but I don't have to pay the VIP costs. I "think" VIP costs locally are ~ $40, closer to $75 for doubles. This would also include dropping off / picking up. If I said all 15 tanks that I have in opperation were $40 / tank, that's another $200 $600 that I didn't have to spend this year.

I still don't think that I'll "break even" or save $, but not being nickel and dimed by the lds, having to pay the tank "tax", getting good fills at my conveinence has made it worth it so far... and I'm not trying to argue with anyone, everyone has made valid points.

You know I had a thought, what would be the best of both worlds is if you owned a few bank bottles and had a service that would come around once a month for a fee to top them off, or maybe a will call service. Our local fire departments all do that. So instead of them each having a compressor they just get the banks topped off every so often. No maintinence, not really any overhead. For the average diver they'd have less than $1K invested and all the air they could ever want.... just thinking out loud. There's not enough divers in my area to warrant something like that (at least I don't think).

Edit: huge mathematical error up top... not sure what happened there, lol... $40 * 15 tanks...