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Demand valve


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If I get a demand valve which can deliver up to 40LPM , can I connect it to a regulator with a HISS that has a setting up tp 25LPM=max regulator setting  ,while still getting 40LMP from a demand valve?

I wanna get demand valve and new regulators.




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There seem to be people who disagree with me about this, but my answer is yes/no.  Yes to the important parts -- a demand valve attached to a DISS fitting will bypass the lpm settings on your regulator, and most importantly, yes, you will get as much O2 as you need every time you need it just by inhaling. 

This second part is not relevant to the "yesses" I just stated, but it's of interest to me, and I will be happy to be corrected if I am wrong.  I think lpm stops being meaningful when you are using a demand valve.  Think of the typical mask with a reservoir bag.  The lpm determines how fast the bag gets filled, but when you breathe in, you are not breathing the O2 in at the rate it came into the bag (the lpm that your regulator is set to), you're breathing it in at whatever rate your inhalation creates.  With a demand valve, the O2 is always available, so there's no bag to fill, and therefore no relevance to flow rate in that regard.  Similarly, as with a bag-based mask, when you breathe in, you are breathing in at whatever "flow rate" your inhalation creates.  Doesn't matter what it is; the oxygen will always be there for you.



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thanks for the replies, the DISS was more important for me to know.

I Was looking at a demand valve that had a limit of 40/LPM so I thought it was somehow depended on the regulator used with it.

But with more research I found that there are also 160/LPM demand valves. 

So there really is a limit ,but it is set by the specific type of demand valve.


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Hi John,

The only correction I will make to this topic is that not all regulators that have a DISS connection bypass the LPM setting. There are many flavors out there. There are regulators that have two air ports and both may have DISS connections (see attached picture). There are also those that have one DISS connection but no LPM adjustment.
If you have a two port model, the port beneath the pressure gauge will be the 50 PSI port. If your DISS is at the end near the LPM dial it is controlled by the dial and it probably will not work well with the demand valve.  I posted this on the Facebook group. Its everything you need for a "E" tank, including the regulator, mask, hose, and demand valve.

The seller told me he has several to sell and will relist when this one sells. I say this because I hate to see a couple of clusterheads get into a bidding war.
Please note in the instructions about shipping. I was the first to buy from him and asked he throw everything in a medium flat rate box. I was the only bidder and got mine for $112 with shipping.
EBAY Demand Valve listing


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