Trimix better tanks, HP or LP?

[Blacthorn]

Hi,

I was talking to a LDS today and they said that if you are going dive trimix it is better (or at least more benfical) to use LP tanks instead of HP tanks. I was wondering if this was true, and the reasons behind it if it is. Or the reasons for it not being true.

Thanks

 

[Jimmer]

Well they say it's easier to PP blend in an LP tank. But if the shop has a booster or continuously blends, then who cares. I know up here in my area of the great lakes, HP tanks are definetly preffered amongst the tech divers. You also have to remember that HP130's and LP104's are the same size, and at a given pressure have about the same amount of gas. So the HP tanks are basically LP tanks with a legal overfill.

 

[Dive-aholic]

Based on where you're at, it really doesn't matter which tanks you get. You're close enough to shops where it doesn't matter. My suggestion is to find a shop that has the capability to blend mix without needing to worry whether you have LPs or HPs. Jimmer got it right about the booster. It sounds like your shop will only fill LPs to 2400. That's fine, but if they won't buy a booster to do proper blending, then what else are they skimming on? Oh, and BTW, there's nothing illegal about overfills.

 

[limeyx]

Hi,

I was talking to a LDS today and they said that if you are going dive trimix it is better (or at least more benfical) to use LP tanks instead of HP tanks. I was wondering if this was true, and the reasons behind it if it is. Or the reasons for it not being true.

Thanks

This has been discussed a million times already with greatly varying results
You can do a search to dig up the history on it....

Basically what you need to do is

1) decide how much gas you want (this will limit the tanks you want)
2) from that list, make sure you can get decent fills from the places you care about (this may limit the options even more)
3) try some as all doubles trim out differently on different people (some like longer tanks, some like shorter and lighter)
4) see if any fit your budget

Traditionally people say LP tanks are "easier" to partial pressure fill, but that means you need a physically bigger tank than an HP tank rated to the same amount of gas (i.e. an LP80 is bigger physically than an HP80) so you may carry more weight in the tank (and maybe more lead to sink it)

Also, a lot of tanks are "paired" with the same physical size tank in LP and HP
e.g. an LP80 is the same size approx as an HP100
a LP95 is same as HP119
a LP104 is an HP130

so would you rather have a "full" LP95 with 95cft or a "not full" 119 with 95 cft sometimes from crappy stores but 119 cft from a good fill ? The point being "full" is all relative. Simply saying I like LP better as I get a "full" fill is less relevant than how much gas you actually have.

HP tanks for the same size generally cost more (i.e. an HP100 is usually more expensive than an LP80) so cost can be an issue.

of course it is all (once again) made more complex in that some stores/areas of the world routinely overfill LP tanks to the same pressures as HP tanks. This is not condoned by tank manufacturers, but does happen.