Laundry Detergent Cup Drain w/Backstop - v4.1

Laundry Detergent Cap Drain Accessory – Latest (and Hopefully Final) Design

After experimenting with various detergent and fabric softener containers, I’ve settled on a more configurable, future-proof design. This version combines proven features from earlier iterations with a few key improvements.

The design now consists of three parts:

Cup_Funnel – A universal, one-size-fits-all part with a rounded design for reduced material used and faster print time.

*_Cap – Custom-sized to fit the neck of each jug.

*_Bushing– Bridges the funnel’s drain tube to the screw cap, allowing compatibility with various jug neck sizes.

Select the cap and bushing brand that matches your product. If your product isn’t listed in the configuration table, find the dimensions that most closely match your jug’s neck. If no close match is available, contact me with your product’s name and dimensions (as shown in the configuration table), and I’ll create a new set to fit your product and add them to this table.

All parts are printed separately and assembled afterward. The Cup_Funnel flange from earlier designs has been removed, and there’s no longer a pause mid-print to insert the cap.  

The cap is no longer captive,  So if you change products -  You can just print a new cap and bushing as needed.

Assembly Instructions

Once the parts are printed, clean up any stringing and smooth any rough edges.

Slide the screw cap onto the funnel’s drain tube.

Slide the bushing onto the drain tube, aligning its gap with the funnel’s drip spout. Ensure the large flat side faces the screw cap.

Push the bushing past the drain spout, then rotate it ~180° so the gap aligns with the tube’s key.

Refer to the assembly diagram in the images for visual guidance.

Important Note

Jug neck sizes vary between brands. Check the Cap Design Table in the images to find the closest match for your container. 
If none of the listed caps fit, provide the dimensions shown in the Cap Design Table, and I can create a new screw-cap and bushing to fit your jug.

Printing Guidelines

Funnel – Since the screw-cap and bushing are removable, you can take the time to print the funnel in high quality. I used PLA with a standard print profile, a 0.4 mm nozzle, and a 0.15 mm layer height for a cleaner, more polished finish.

Screw Cap & Bushing – I print these in PETG for added strength, using a standard profile with a 0.4 mm nozzle and 0.15 mm layer height for stronger, cleaner threads. PLA works just as well in most cases, but I did manage to crack a cap by over-tightening - so the choice is yours.

Updates:

10-06-2025 – All new models were uploaded. The latest screw cap for the Kirkland Ultra Clean jug measured an inside neck diameter of 25.7 mm. The funnel drain tube had an outside diameter of 25 mm, which did not provide sufficient clearance for the bushing. As a result, the drain tube diameter needed to be reduced.

10-06-2025 - Added screw cap and bushing for Kirkland Ultra Clean jug.