Safety of using an aquarium pump as a toy
January 19, 2017 8:36 PM   Subscribe

My two-year-old loves to play in running faucets for long periods of time (usually "washing" things like plastic plates or his hands), but I don't like to let the water run indefinitely for cost and conservation reasons. I got this little aquarium pump and it has nicely solved this problem. I fill the sink, stick the pump in and attach aquarium tubing to it, and he uses the tubing like a hose to do his "washing".

Are there safety risks to doing this? I'm thinking mainly of electrical shocks if the unit malfunctions. There don't seem to be moving parts (like fans or blades) that he could touch. The unit does get somewhat hot sometimes, but not such that it would burn him. He's supervised when he's using it, so I'm less worried about stuff he could do to the unit, and more about if the unit could malfunction and shock him suddenly.
posted by ABCApplePie to Pets & Animals (10 answers total) 1 user marked this as a favorite
In reflecting on this, I may have sort of answered my own question... I think I'll just put the pump in a separate plastic bin of water, then let him have access to the tubing only, so he's not directly exposed to the pool the pump is in at all.

I'd still be interested to hear the answer to my original question, however.
posted by ABCApplePie at 8:47 PM on January 19, 2017

I use little pumps like this for many purposes and haven't killed a fish or cat yet. However, it is very important the pump not be allowed to run dry (meaning lifted out of water while running). There is a moving part inside, a magnetic impeller. Without water to cool it, it heats up to too-hot-to-touch levels quickly. Left running, the pump will do some combination of seizing up, shatter its impeller, melt its plastic housing. I'm not sure what happens to the electricity at that point but wouldn't be super eager to find out.

I let my son play with a similar pump when he was 5-6ish but fixed the pump to the bottom of a tub so it couldn't be lifted out.
posted by jamaro at 8:50 PM on January 19, 2017

I'm an aquarium owner and have never had an issue with something like this shorting, but in your original plan I would worry a bit about eventually working a power cord free of the housing or something. They are robust but aren't designed for constant movement involved in 'play.'

A GFCI would provide added protection--supposedly they cut off power amazingly quickly. One author described idiotically reaching in after a powered on fluorescent fixture he had dropped accidentally into his aquarium and having zero effect because of the GFCI. You can buy extension cords that have a GFCI if the outlet doesn't.
posted by mark k at 9:12 PM on January 19, 2017

A GFCI wouldn't be helpful in this case because the pump does not have a ground lead.

A 120V A/C circuit consists of a hot and a neutral. The "hot" provides one side of 240 volts of alternating current, from -120V to +120V, so that in relation to the neutral, there's something between 0 and 120V of differential. The neutral is always supposed to be at zero volts. Current has to flow back and this happens through the neutral. Inside your circuit breaker box, neutral and ground are wired together.

Many two-wire plugs are polarized to make sure that the riskier side (the hot) is exposed more carefully. For example, in the old days, the metal shell of a table lamp's socket might not be properly insulated, and without a polarized plug, it was possible that you could be energizing the metal shell with 120V so that people could potentially experience a shock if they also happened to touch something grounded while touching the lamp. These days, that's not supposed to happen, because the polarization means that hot is only exposed on the lamp's base terminal.

For some types of appliance, especially containing motors, there is a greater chance of various mechanical failures that could possibly cause the hot to come in contact with the casing. Think, for example, of old power tools. An electric drill with a metal case. The metal case gets connected to ground, which has no voltage potential present, so that if something like a large volume of metal shavings were to get into the brushes and cause a short to the case, or the tool might be used on a wall where someone accidentally drills into an A/C branch circuit, the voltage is safely and immediately siphoned away from the tool-user. This is very different from neutral, which is also at zero volts, because the neutral is part of the circuit and power is always returning to the source via neutral.

So at some point, engineers realized that you could watch for a flow of electricity on the ground, and that this was almost always an indication of a problem, potentially a life-threatening one. So a GFCI will cut off the hot to an outlet if there's any sign of current on the ground.

However, your pump lacks a ground, so a GFCI probably isn't helpful here.

It is worth noting that you are essentially running 120V into a liquid conductor, and this has the potential to be hazardous. These little pumps are designed to be robust as long as they aren't mistreated. Make sure you're inspecting the pump every time you use it to make sure that the cord is in good condition, as someone else implied it should be firmly in the housing, it shouldn't be stressed in any way, the pump should be firmly affixed to minimize movement, and the pump shouldn't be allowed to run dry.

I think this would also be safer where there were not additional grounds within reach. A sink made out of something non-conductive, with PVC drain pipe, with a faucet being fed by plastic supply lines, on a nonconductive floor without other grounds, would mean that even if the hot was exposed to the water, the risk of a human somehow completing the circuit is reduced. This is how birds can safely land on electrical wires.

Kids stick stuff in outlets "all the time" and usually manage to survive, but yes there is some potential for risk here. It's hard to say exactly what the potential for risk is, because it is heavily dependent on the environment and how careful you are.
posted by jgreco at 2:01 AM on January 20, 2017 [3 favorites]

There are plenty of pumps about that run on 12V. Personally I'd be much happier with my kids playing with something like that.
posted by pipeski at 2:53 AM on January 20, 2017

A GFCI wouldn't be helpful in this case because the pump does not have a ground lead.

I just want to correct a small but important misunderstanding here. GFCI protection absolutely does help even in cases where no ground lead is present. In fact, a GFCI outlet is a valid / to-code replacement for old 2-prong outlets on ungrounded circuits. [one source with people saying the same; others]

Specifically, the GFCI protection trips when it detects any difference in current flow between the "hot" and the "neutral" lead, not when it detects current on a ground connection. Think of it this way: the outlet is sending current "out" one wire, and if it doesn't get just about exactly the same amount coming back "in" the other wire, it trips. So if any current at all starts flowing through a person or any other path other than right back into the outlet, the electricity is shut off immediately.

For example, the GFCI built into many hairdryer plugs can save you if you drop your hairdryer while sitting in your bathtub (but please don't do that), even though that plug has no third prong for a ground connection. And so yes, GFCI can provide some additional safety for playing with an aquarium pump.
posted by whatnotever at 6:23 AM on January 20, 2017 [7 favorites]

This toy water pump may be a good choice for you - I haven't used it myself, but I've heard good reviews from folks I trust.
posted by Jaclyn at 7:32 AM on January 20, 2017

Could you get a length of pipe and an auto siphon from the home brew store? That would give him running water with no electricity whatsoever.
posted by Marinara at 8:06 AM on January 20, 2017

Our family has experience with the toy water pump that Jaclyn references. My kid LOVED it and played with it forever. Highly recommend it!
posted by banjonaut at 11:16 AM on January 20, 2017

We also have that pump toy. It's GREAT!
posted by lizifer at 6:12 PM on January 20, 2017

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