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Replace 12VDC Standby Water Pump With a 120VDC Pump - Printable Version

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Replace 12VDC Standby Water Pump With a 120VDC Pump - hypoxia - 04-28-2026

The standby 12VDC water pump doesn't work well with the Royal Flush toilets.  Is there a good reason to keep that system instead of replacing it with a standby 120VAC pump (assuming it fits)?  I just am not thinking of a scenario that takes us down to 12VDC without it being a total disaster regardless of the voltage.  We can normally find a cactus to lean against to resolve that problem Big Grin

RE: Replace 12VDC Standby Water Pump With a 120VDC Pump - HoosierDaddy - 04-28-2026

Jim, 316 has dual 12 volt water pumps. I have been satisfied with performance . We have the Microphor toilet.

RE: Replace 12VDC Standby Water Pump With a 120VDC Pump - Richard - 04-29-2026

Jim, I don’t see any reason to prevent that, other than space for mounting a larger pump. The 12VDC pump was a holdover from earlier vintage. The idea being the 12VDC water pumps and air compressors would be much more efficient when off grid.

I can see where the Headhunter toilet would not work well with the 12VDC pump.

RE: Replace 12VDC Standby Water Pump With a 120VDC Pump - RobSC - 04-29-2026

Jim,

I'm with you on this one.  The 12VDC pump is almost useless with the Royal Flush toilet.  I had to use it when my Headhunter failed.  When you find a solution, I'm going to follow your lead.

RE: Replace 12VDC Standby Water Pump With a 120VDC Pump - hypoxia - 04-30-2026

I replaced the seal in the Headhunter Mach 5 which should resolve the seal sticking problem.  I removed the 12VDC pump along with the associated plumbing.  The backflow valve to the 12VDC pump was stuck open, I removed it and plugged the hole.  There is enough room to reposition the Mach 5 and I added a Grundfos Scala2 120VAC water pump beside it.  The Scala2 will hold a constant 55 psi during a flush unlike the Mach 5 that will go down to around 40 psi before cycling.  I used it for a week & couldn't tell any real difference between the two pumps.  I do not plan to have both connected to the plumbing, I'll have the piping set up to where I can connect one or the other.  Chances of actually needing a backup are fairly small.

Historically, the Scala2 has been problematic with seal leaks, Grundfos has been addressing the issue with design changes, hopefully this late version is resolved.  It has a 3 year warranty.  Parts are readily available.  Home Depot Scala2  FWIW, I purchased through the  Military Exchange Home Depot storefront, 10% off & no sales tax = less than One Newell Unit.