Regulator Tuning

[mainedvr]

Recently I have switched to the HOG D1 cold water first stage, I am using an A700 for a primary and now have a DR 3000 series second stage for my back up. I was previously using the MK25 as my first stage but since my wife and I each needed two first for our cave courses coming up she is going to use two mk25's and I am going to use two of the D1's.

My question is when we had our regs servcied mine were on the mk25 and now on the D1, should my second stages be tuned to my first stages? Or are the specs similar that it should not matter. Everything breaths great have used them down to 50' no free flows or weeping, so I am not thinking it's an issue but hate to get to cave country and find it may be while in a cave.

Thanks

 

[spectrum]

Technically yes they should be tuned for the IP of your first stage but you jumped ahead with an ad hoc test. If they are not prone to free flow and breathe as good as ever I'd leave them alone.

Pete

 

[DA Aquamaster]

I set the IP on my regs to the same IP to allow them to be switched without any issues.

However, both second stages you mentioned are balanced, so the change in IP needs to be pretty significant before the downstream bias in the second stage causes the second stage to free flow as an overpressure function. In most cases the IP will be 135-145 psi and a balanced second stage won't free flow until the IP is around 170-180 psi. Even if you have one balanced second stage tuned to a reg with an IP down around 125 psi, and run it at 145 psi, it still usually won't free flow.

With a nicely tuned unbalanced second stage however free flow can be an issue.

 

[mainedvr]

Thanks for the quick responses, when I bought the regs I was trying to find the specs but I guess that is a closely guarded secret . We did take the regs out for a few shallow dives before heading to a deeper site so felt comfortable with the set up. Will have them tuned before our courses in November anyhow just did not want to do it now and then again in a two months unless needed.

 

[divad]

The SP IP spec is 135 (I've read). Make an IP gauge and put it on the D1 to satisfy your curiosity.