Underwater Junction Box for Fountain Lights – EasyPro

An underwater junction box for fountain lights solves one of the most common wiring headaches in fountain installation: how do you safely connect multiple submersible lights to a single power supply without a tangle of exposed connections sitting on the pond floor? The EasyPro bronze junction box gives you a single sealed hub — all your light leads run into one corrosion-resistant bronze enclosure, filled with potting compound, and locked watertight.

Smith Creek Field Notes

When we install pond and lake fountains here in New York, the junction box is one of those components people try to skip or substitute — and it's almost always where problems start. Bronze matters here. We've pulled plastic alternatives out of ponds after a single winter and they're cracked or corroded at every port. The bronze construction and compression-sealed ports on these EasyPro boxes hold up season after season. Don't skip the potting compound either — it's not optional. A box installed dry will leak at the wire entries eventually. Fill it completely, let it cure, and you're done.

Is This Right for Your Pond Fountain?

✅ Use this underwater junction box for fountain lights if:

• You're wiring 2–8 individual submersible lights to a single transformer or power supply
• You want a clean, professional installation with a single sealed connection point underwater
• You're mounting to a flange or base plate — choose the 1" FPT bottom inlet version (UJ4B or UJ8B)
• You're building a new fountain lighting display or upgrading existing wiring

⚠️ Keep in mind:

• Potting compound (UJC) is required — the box is not waterproof without it
• Side ports accept wires 3/8" diameter or smaller
• Choose 4-outlet (UJ4/UJ4B) for smaller displays; 8-outlet (UJ8/UJ8B) for larger multi-light setups
• Not sure which configuration fits your project? Call us: (833) 326-5253

Specifications

All models: compression-sealed side ports, max wire diameter 3/8", bronze construction.

Bottom Inlet vs. No Bottom Inlet — Which Do You Need?

The no-inlet versions (UJ4, UJ8) have a solid bottom. All wire connections — including your power feed — enter through the side compression ports. This works well for standard installations where wiring runs horizontally along the pond floor.

The bottom inlet versions (UJ4B, UJ8B) have a 1" female pipe thread (FPT) opening in the base. This lets you mount the box directly onto a bronze flange (such as the EasyPro BWF10), with power feed rising up through the bottom and light leads entering from the sides. This is the cleaner, more professional choice for permanent fountain installations.

Required: Potting Compound

The EasyPro UJC Flexible Potting Compound is the only recommended method for sealing this underwater junction box for fountain lights. Once your wires are connected and routed, fill the box completely before closing. The re-enterable formula behaves similarly to silicone caulk — it can be removed and reworked if you need to adjust wiring later. Each 385 mL container fills one UJ8 or UJ8B box, or two UJ4 or UJ4B boxes. Butyl tape is included with the compound to seal any unused ports. The UJC potting compound is available as a separate variant on this page.

Pair With Fountain Lighting

This junction box is a wiring component — you'll need submersible light fixtures to go with it. Browse our full pond and lake fountain lighting collection, including the EasyPro color changing fountain light kit and the EasyPro stainless steel LED fountain light kit. Also explore our pond and lake fountains collection and fountain nozzles and parts.

Frequently Asked Questions

What is an underwater junction box for fountain lights used for?

An underwater junction box for fountain lights consolidates the wiring from multiple submersible fixtures into a single sealed enclosure. Instead of running each light's lead all the way back to a transformer, you join them at a central hub underwater — fewer exposed connections, cleaner installation, and one sealed watertight point to maintain.

Do I need potting compound to make the junction box waterproof?

Yes — the box is not watertight without it. EasyPro states that potting compound is the only recommended means of creating a watertight seal. The UJC compound is sold separately and is available as a variant on this page.

What's the difference between the UJ4 and UJ8?

The UJ4 has 4 outlet ports for smaller displays with up to 4 lights. The UJ8 has 8 outlet ports for larger multi-light installations. Both are available with or without a 1" threaded bottom inlet.

When should I choose the bottom inlet version (UJ4B or UJ8B)?

Choose the bottom inlet version when mounting the box onto a bronze flange such as the EasyPro BWF10, with your power feed entering from below. It creates a cleaner installation and is the preferred option for permanent fountain builds. Note that the bottom inlet versions are taller — 2 7/8" vs 1 7/8" for the 4-outlet models, and 2 7/8" vs 2" for the 8-outlet models — so factor that into your mounting plan.

What size wires fit through the compression ports?

The side compression ports accept wires up to 3/8" in diameter. Standard submersible fountain light cables fit without issue.

Can I reopen the junction box after filling it with potting compound?

Yes. The EasyPro UJC compound is re-enterable — it can be cut out or removed if you need to change wiring. It's not a permanent epoxy. Once you've made adjustments, refill with fresh compound to reseal.

How much potting compound do I need?

One 385 mL UJC container fills one UJ8 or UJ8B box, or two UJ4 or UJ4B boxes. Order accordingly if you're installing multiple junction boxes on the same project.

Is this junction box compatible with all EasyPro fountain lights?

Yes — this is the EasyPro-designed wiring hub for their underwater lighting systems. It's also compatible with other brands as long as wire diameter is 3/8" or smaller.

Can I use this above water or in outdoor above-grade installations?

These boxes are designed for submersible underwater use, but the bronze construction and compression-sealed ports make them suitable for any wet outdoor environment. Always fill with potting compound regardless of installation location for a proper weatherproof seal.

Does the junction box come with anything, or do I need to buy accessories separately?

The junction box itself is included. Butyl tape to seal unused ports comes with the UJC potting compound kit. The potting compound is required for a waterproof installation and is available as a variant on this page.

Seasonal Notes

Spring

When bringing your fountain system back online after winter, inspect the junction box before powering up. Check that the potting compound seal is intact at all wire entries and that no ports have shifted. Bronze holds up through freeze-thaw cycles, but a quick visual check before the season starts is good practice.

Summer

Peak season for fountain operation. Once installed and sealed, the junction box requires no maintenance. If you're adding lights mid-season, the re-enterable potting compound makes it easy to open, add a wire, and reseal without pulling the entire system.

Fall

If shutting down your fountain for winter, remove the junction box if possible and store it dry. Inspect the compound seal and address any loose ports before putting it back in service next spring.

Winter

Water trapped inside an unsealed box will expand when it freezes and can crack ports or push seals loose. Always ensure the box is fully filled with potting compound before leaving it submerged through winter — or remove it entirely during off-season storage.

Browse Related Products

Shop our full pond and lake fountain lighting collection, explore fountain nozzles and parts, or browse all pond and lake fountain systems. Questions? Call us at (833) 326-5253.