Water table circulation pump

This design adds a pump to a children’s water table. It uses a low cost submersible pump, and some flexible tubing (ID-5/16”, OD 7/16”) to pump water from the water table’s drain up to the top feature.

Using a 12V pump and a battery renders it safe, in my case I used a 5V 2A power bank boosted to 12V with a MT3608 boost module so that it is portable and not connected to the mains supply at all. A container for a MT3608 module, that can be waterproofed easily, is included.

Printing:

I used 0.16mm layers with adaptive height. This prints the threads so that they aren’t too tight. If they are tight you can reduce the thread size with a file or print the nut very slightly larger (1%). Some silicone or similar grease will help the parts thread together.

I use supports for the smaller (non submersible pump) adapter. This generates very little support and makes for a better version of the filter where it seats against the top of the threaded section. Be sure to remember to remove all supports, some will be inside the parts.

The elbow is printed at an angle to preserve accuracy of the parts that fit together.

To assemble:

Add a length of tubing to the outlet port, make it long enough to reach the height of the top feature.

Couple the elbow to the pump inlet using a 15 to 18mm section of plastic tubing

Add silicone caulking to the elbow (small amount, don’t block the hole with caulking) and to the bottom hole of the adapter. Now position the pump to line up with the inlet and outlet ports.

Add the strap and screw the pump to the adapter using 2 plastic screws or M3 screws. If they are too tight, heat for 4 seconds with a soldering iron then screw them in.

The filter uses a 150mm x 9mm section of the scourer pad. It is held in place by the short guide sections in the bottom section of the filter. Move the ends so that they are covered by a vertical section in the outer wall.

To use it

Simply unscrew the black drain plug and insert the assembled pump. The tubing runs up through the centre of the assembly and hooks onto the top feature. Water is filtered by the side entry filter which uses a short piece of a scourer pad as the filter element.

Use silicone sealant or caulking under the flat nut and do not overtighten.

The screw section is designed for my water table which has a 22mm thick base. Some versions have only a single layer and the screw is too long.  It needs to be as short as possible so that the filter is always submerged

• You can shorten the screw in the slicer or

• cut it off afterwards.

• Print 2 nuts and use one below and one above the bottom of the water table, seal both surfaces.

Other

When the flow is diminished, replace or clean the filter.

My pump draws a bit more than 1A from a 5V power bank, be sure to get a power bank that can supply more than 1A (eg. 10W rating which would give 2A maximum), most are rated 1A and will just shut down after a few seconds.

For 5 hours of use you need a 5000mAH capacity. For 2 hours you need 2000mAH capacity.

These pumps need to be full of water to operate. If air is trapped in the pump part, it won’t cause any flow. This is why the design has the pump at the lowest point where it will always fill with water.

I’ve included some design and step files if you want to modify it.

A complete, self priming and rechargeable pump can be purchased at a decent price, this is likely a better way to go.

Other pumps

You may find a cat water fountain pump that looks similar but has only 1 outlet. These are supposed to be submerged. It may not have enough pressure to pump water all the way to the top feature.  They often run from 5V, I suggest you find a 12V or even 9V pump with a rated head of at least 2m.

For a submersible pump (including the one I refenced above) you can use the container version of the drain adapter. This will need to have the wire brought out and sealed through the hole in the container. This container fills with water when in use.