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I just had the Zoeller 507 battery powered backup sump pump installed by a plumber. After the install, I asked the plumber whether the battery was conventional lead acid or "maintenance free" AGM (the manual says that it can use both). He told me it was maintenance free.
But when I opened the plastic box that housed the battery I noticed that it was Interstate SRM-27, a wet/acid deep cycle marine battery. Apparently it has to be checked every month for the water level and topped off. What is worse, potentially, he installed the battery 1 foot away from my gas water heater, which has an open pilot flame. The whole set up is in my hvac closet, which is crowded.
Everything I read online says that wet/acid battery will offgas hydrogen which is highly flammable/explosive. So is the battery a fire/explosion hazard? Should I call my plumber back and request that he replace it with a safer "sealed" AGM battery that is both maintenance free and doesn't offgas (much) hydrogen?
If there is someone here who is knowledgable about this, I'd really appreciate some advice. Am I worrying over nothing or did my plumber do a shoddy/cheap job with the battery?
The rate of hydrogen production is so minute as to be utterly inconsequential. Further, hydrogen, as the least dense element, will never "pool" like methane and there is no real risk of of having the sump pump back-up battery cause any sort of explosion.
You may track down some article about a commercial data center backup (where they literally have HUNDREDS of batteries set up to charge continuously) being an explosion risk but those same articles will state the there was willful disregard for ignoring DAYS of gas detector alerts and/or faulty ventilation.
Your plumber cheaped out. The hydrogen gas possibility in a sealed box is there, but the amount of energy in an explosion would be minor. However... there are other issues that are much more important.
1. Lead acid automotive and marine batteries create a "cloud" of hydrochloric acid in the charging and discharge process. It will promote rust and corrosion or worse. I stored four marine batteries on my deck for a year a while back. They weren't leaking, just sitting there and exposed to the rain and elements. I have had to replace the three deck boards they were sitting on because of extreme rot where they were sitting. Batteries I stored inside under a metal leg table rusted the legs of the table.
2. A shorted cell in a battery can under certain circumstances lead to the battery being overcharged and heating enough to explode. My wife bought a car where that had happened, and even though it had been thoroughly hosed down and cleaned up, there were CONSTANT problems with rust and wiring going bad. A battery explosion is a BIG deal.
Even if the battery you have is good, I would replace it with an AGM sealed one. Knowing what I know now, I would sooner keep a propane tank (with an extra shutoff for safety) in the house than a lead acid automotive or marine or deep cycle battery. Sealed is the ONLY way to go in a home.
One response says it's fine/safe, another says that sealed is the only way to go inside the house.
Now, I am really confused.
Is there any plumber out there? Is the flooded lead acid battery setup for a backup sump pump (even next to a water heater) a pretty standard setup?
The battery, by the way, is inside a black plastic box and is being constantly (trickle?) charged by the Zoeller backup pump charger (I think it's a smart charger - it has a screen and tells me voltage and when there was loss of power, etc.; the voltage says 13.09).
The whole setup (HVAC, water heater, sump pit) is in my finished basement next to my TV area and kids play area.
It is completely standard to use a traditional lead acid battery for sump pump back-up -- Battery Backup Sump Pump Buyer's Guide - How to Pick the Perfect Battery Backup Sump Pump Probably 95% of folks with basements have this sort of setup -- utility space is where the furnace, water heater, sump and backup are, kids play area/ dad's sports zone is other the side of interior grade wall. No concerns about "corrosive cloud" with any monitor charger that has a monitor to prevent overvoltage!
The power density and low cost of deep cycle marine style batteries is hard to beat.
Anyone that is being honest about AGM or other battery types, like gel cell, will admit that they can and do off gas, especially if overcharged, and their higher cost makes them a poor choice for things like sump pump back up, where it is easy to go to the WalMart when ever needed and buy a simple replacement -- Gel vs. AGM vs. Wet Cell Batteries | Solarcraft
Sorry Chet, real world experience tells me otherwise. I've seen people really believe theories and book specs get whapped up the side of the head. One of the funnier ones the TMEN and the famous Minto Wheel debacle.
You get right down to it though and on municipal water service I would remove the battery powered pump and replace it with a water-powered eductor pump. A battery holds about the energy equivalent of a cup of gasoline. That won't last long in a real power outage.
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What a hydrogen fire might look like
