Replacing tank on vfd

**greenmonster304** · 03-02-2012, 07:12 AM

The tank for my vfd started to leak so I want to replace it but I am not sure what pressure to charge the new tank to. I wasnt sure if the vfd tanks get charged differently. Thanks in advance for your help.

**valveman** · 03-02-2012, 08:15 AM

The tank precharge is usually about 30% less than the running pressure.

**JPat** · 03-05-2012, 01:24 PM

Hmmm. Every VFD we have installed, the manufacturer recommends 70% air pressure to running pressure...Doing the math for you; if your running pressure is 60psi the pre-charge in the tank should be 42psi.

**valveman** · 03-05-2012, 02:57 PM

Hi JPat. Doing the math I think 70% of, or 30% less than 60 is still the same 42 PSI. The real question is why did the tank go bad?

**JPat** · 03-07-2012, 12:17 PM

Meh, tanks go bad all the time. The rubber that most companies are using is recycled... "Do it yourself" tanks have a high failure rate as well. 5yr warranty on all tanks!!!

**valveman** · 03-07-2012, 04:18 PM

Bladder or diaphragm type tanks only go bad for two reasons. Either they rust through, or the bladder breaks. Most of the busted bladders I see on tanks with a VFD, are from the pump not shutting off when it should, causing the pressure to spike and bust the bladder.

One of the big box stores has a 32 gallon tank with a lifetime warranty. I guess it doesn’t have recycled rubber.

**Texas Wellman** · 03-07-2012, 08:33 PM

"Lifetime warranty"...when it breaks, the life is over!!

**greenmonster304** · 03-08-2012, 04:38 AM

The tank rusted out because it was in a pit that was always damp.

**valveman** · 03-08-2012, 07:10 AM

Originally Posted by greenmonster304

The tank rusted out because it was in a pit that was always damp.

Good to know. These are the kind of installations that can benefit from a fiberglass tank.

Yeah "lifetime warranty". Can you believe that? I think the company might just change names every few years to get out of warranties.