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Question DetailsAsked on 4/10/2015

Can the battery backup sump pump be housed in a flood control basin and electronically connected inside the well?

I'm trying to avoid any demolition inside the home, i.e., demolishing drywall to run electrical lines in order to connect the battery backup sump pump to the existing flood control system that is located in the front yard.. There is an outlet inside the flood control basin/well. Is it possible to make all connections inside the basin? Is it possible to install a shelf inside the basin to keep the backup battery free of debris?

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Technically possible - yes. Economically feasible for a residential situation, or likely to be accepted by local code enforcement agency - likely no. I have done that type of installation on in-ground monitoring systems and drainage sump work on commercial jobs where the installation of the alarming and pump and backup systems ran into the several thousands even with a normal house-sized sump pump.

Installing a shelf/batery box should be no problem, but would likely have to be easily removeable from above (like hanging from the lip or fitting into near-flush brackets) to allow full diameter access to the well for cleaning and sump pump maintenance/ installation when needed.

The big problem is normal batteries outgas explosive hydrogen gas, as well as hydrogen sulfide and sulfuric acid gas in small amounts (which will corrode wiring and pumps/motors), so not only would EVERYTHING in the wetwell have to be upgraded to explosive environment electrical class, but by code you would also have to have a blower unit to prevent explosive levels of gas from building up, which means either circulating probably seasonally freezing air in the well (bad idea for obvious reasons) or having to have an explosion-proof heated forced air unit. You could get around that by using a more expensive remote site lithium or similar sealed battery that does not outgas - but they are pricey. Also, your plan would also require that the charger be in the damp environment - calling for a wet environment expensive charger and more chance of failure due to corrosion/wet connections.

Even if that could work, unless your area is constantly above about 50-60 degrees (accounting for maybe 10 degrees of battery heating from the trickle charging), the battery would be in a cold environment so its functional life would be much less than if it were indoors - at least at the start of a power outage, until the interior of the house cooled down due to loss of heat, but by that time the battery would likely be dead too unless recharged off a generator. At cold temperatures the battery life drops way off - I don't remember the numbers exactly, but at zero F you get about 75% of the 77F (25 celsius) "rated" battery life, about 50% at -20F, and about 20% at -40F - in rough numbers. If the battery freezes solid due to low charge it is usually shot and has to be replaced, so that is a cost factor too.

I would just find a safe, suitable place inside the heated part of the house for the charger/battery, then run a line out through the wall from there and either in conduit along the wall/foundation (above any wetting level) and then in conduit or direct burial cable to the wet well. That way your drywall damage would be limited to maybe a new GFCI outlet for it tapping off either an existing circuit at that location or placing it very near the breaker panel for its power run, and a small hole through the wall. Of course, because you are presumably talking 12V or 24V backup battery, you will want to keep the run as short as possible and will need large wiring to limit line losses in the run to the pump.

One other consideration in these types of backup systems, especially if you are not up to carrying a batteary around, is either running a charging cable or locating it (if feasible) where jumper cables from a car (assuming it is 12V battery) can be connected to it to recharge it during a power outage. I have designed this type of recharge wiring from gas boiler backup batteries to the front wall of garages with terminal posts so battery jumper cables could be hooked up to recharge a discharged backup battery. Of course, full disconnect from the house current is necessary in that case.

Another alternative that does not get away from the wiring run from the house but does limit the wire size, is installing a heated battery box outside the wet well, like the ones made for auto-start equipment like generators and for emergency backup animal watering devices and brooder heat lamps at farms. Of course, once the power goes off, the battery starts getting cold so it quickly starts losing reserve power capacity.

Your electrician would have to check the code for your area on whether it will require a separate circuit or not - always a good idea anyway if possible so an accidental trip-out on the circuit from another use does not take out your backup system.

One other thing - the battery charger should have either a separate or internal diode system that prevents the battery from discharging into the household wiring. SOOOO many of these systems forget that, so when the house power goes out, the battery just does a rapid discharge into the house wiring through the charger (commonly frying the charger and/or the battery) making it useless as a backup power source.

Another factor you might have forgotten - presumably you have a high level warning system in case the water level rises above the main and/or emergency pump turn-on point, and probably a power-on status light and a failure alarm and maybe an emergency pump-running light - and these alarms need to be where they are readily seen/heard in the house. So, running them also has to be considered, because those alarms should probably be near the main living floor hall or main junction area between rooms; or else right outside the master bedroom so it can be heard clearly both in daytime and night. Or else run to your home alarm or autodial system, if you have one.

My recommnedation - find someone who does a lot of these - may be a plumber, may well (no pun intended) be a Wells and Pumps contractor, as I doubt a normal electrician will feel comfortable with this, especially with the necessary alarm wiring and such. Plus you need a plumber or well guy for the backup pump installation anyway.

One other recommnedation - if at all possible, assuming this well is more than a couple of feet deep, is to go with pumps with flexible discharge hose or readily disconnectable riser pipes that can be pulled from the surface rather than having to climb down into the well, especially if it classifies as a Confined Space Entry under OSHA - which it generally would if a person if able to climb down inside it to work.

And of course, one last thing - be sure the discharges from the pumps are installed such that they are frost protected, so they do not freeze up and plug off when they are needed.

One more after-thought - just so you remember to think outside the box - if your house uses a french drain system for basement flood control like it sounds like, that does not mean the backup sump pump cannot actually be inside the house in an indoor sump (which avoids a lot of the aforementioned issues) - depending on how free-flowing the fill under your basement slab is, and on whether it already has underdrains and a sump. Some house tht have gone to an outdoor wetwell because of excessive inflow have an abandoned underslab drain system that might work as an emergency backup system - as-is or with a deeper sump as applicable. Just a possibility, especially if you have freezing outdoor conditions with any regularity.

Answered 4 years ago by LCD

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