DEL Ozone MCD-50 Replacement: Renewal Kits, Compatible Ozonators and Your Options in 2026

Written by
Delozone Editorial Team

Last updated: September 26, 2026

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The DEL Ozone MCD-50 was fitted to a huge number of portable spas, so it is one of the most common ozonators people end up trying to replace. The trouble is that the original unit and its renewal kit are now hard to find. This guide explains how to tell whether your MCD-50 has actually failed, what can still be repaired, and which replacements make sense in 2026.

What the MCD-50 is

The MCD-50 is a compact corona discharge ozonator for hot tubs up to roughly 1,000 gallons. CMP, which now owns the DEL Ozone brand, lists it with patented APG ozone cells producing about 50 to 70 mg of ozone per hour at rated airflow, and an LED that shows when the generator is running. It shipped in several versions: 120V, 240V and dual-voltage “U” models, with AMP, mini-JJ or hardwired connections depending on the spa maker.

The design is modular. The ozone cell and the power supply are separate parts, which is why DEL sold a renewal kit rather than expecting owners to replace the whole unit. Retailers that stock it describe a typical service life of five years or more before the cell needs renewing.

Is your MCD-50 actually dead?

Before you buy anything, rule out the cheaper problems. In practice, the parts around the ozonator fail more often than the ozonator itself.

1. Check the LED. If the indicator is off while the circulation pump is running, check the breaker, the connector and the fuse before blaming the cell.
2. Look for fine bubbles. With the pump running, you should see a stream of very fine bubbles at the ozone injection point. No bubbles usually means a blocked injector, a stuck check valve or a disconnected hose rather than a failed cell.
3. Inspect the check valve and tubing. If water has backed up into the ozone line, the check valve has failed, and water in the line can damage the cell. Brittle, cracked or discoloured tubing should be replaced with ozone-resistant tubing.
4. Test the water. Ozone test strips give a rough reading, and an ORP meter shows whether oxidation in the water has dropped compared with when the spa was new. Our spa ozonator test guide walks through each check.

Ozone test strips on Amazon Replacement check valves on Amazon

Your three replacement options

Option 1: renewing the cell

DEL’s original MCD-50 renewal kit (part 09-0743-01) included a replacement ozone cell, fuse, hose barb, O-ring, check valve and a short length of tubing. It is now listed as out of stock or discontinued at most retailers. The newer APG module, part 9-1056-01, is the one you are most likely to find, including aftermarket versions made to fit the MCD-50, the EC-10/20/40 Eclipse units and the DEL Ozone 25/50/100.

The swap is a simple job for most owners, based on the steps published by spa parts retailers:

1. Turn off power to the spa at the breaker.
2. Disconnect the ozone tubing from the outlet hose barb on the ozonator.
3. Remove the mounting screw and take the unit out of the equipment bay.
4. Open the housing, unplug the old cell and fit the new module in the same orientation.
5. Replace the check valve and any tubing that looks stiff or discoloured while you are there.
6. Reassemble, restore power, and confirm the LED is on and fine bubbles appear at the injector.

If you are not comfortable working near spa electrics, a spa technician can do this in a short service visit.

Option 2: replacing the whole ozonator

If the unit is water-damaged, the power supply has failed, or the MCD-50 is simply very old, replacing the whole ozonator is usually the better use of money. The key checks are:

• Connector: AMP, mini-JJ or hardwired. Look at the plug on your current unit and at the matching socket on the spa pack.
• Voltage: most portable spas use 120V or 240V for accessories. The MCD-50 label shows which version you have.
• Ozone line: your spa should already have an ozone injector and tubing. Keep the check valve in the line and orient it the right way.
• Output: for a typical 300 to 500 gallon spa, a corona discharge unit in the same 50 mg/hr class as the MCD-50 is the right size.

We compare the current options by connector and fit in the best hot tub ozone generators.

Check HCD-55 style ozonator price on Amazon

Option 3: going back to DEL

DEL Ozone is now part of CMP (Custom Molded Products). CMP’s current DEL Ozone Spa unit is rated for spas up to about 1,000 gallons, has adjustable output around 50 mg/hr and is very compact, so it fits the same equipment bays as the MCD-50. It is mostly sold through spa dealers and pool supply stores, which is useful if you want someone to install and support it. For model details, see our DEL Ozone model guide.

Keeping the new unit working

• Replace the check valve whenever you replace or renew the ozonator; it is cheap and it protects the cell.
• Use ozone-resistant tubing. Ordinary vinyl hardens and cracks, and our ozone material compatibility chart shows what lasts.
• Keep the injector clear. Scale and debris at the venturi stop ozone from reaching the water even when the cell is fine.
• Remember that ozone supplements your sanitizer. Keep testing chlorine or bromine; see how often ozone generators need replacing for a maintenance schedule.

FAQ

Is the DEL MCD-50 discontinued?

Yes. Several spa parts retailers list the MCD-50 and its original renewal kit as discontinued or out of stock. Compatible 9-1056-01 modules and the current CMP DEL Ozone Spa unit are the main ways to keep a DEL setup running.

How long does an MCD-50 last?

Retailers describe a typical run of five years or more before the cell needs renewing. How long yours lasts depends on run time, humidity in the equipment bay and whether water has ever backed up into the ozone line.

Can I use a different brand of ozonator on a spa that had an MCD-50?

Usually, yes, as long as the connector, voltage and mounting fit, and the spa already has an ozone injector. Keep the check valve in place and match the output to your spa size.

Do I need an ozonator at all?

No, it is optional. Without it you will simply need more chlorine or bromine to keep the water clear, and the water may feel and smell more chemical. Most owners who have had one working notice the difference when it fails.

About the Author

Delozone Editorial Team

Editorial Team · Last updated: September 26, 2026

The Delozone Editorial Team researches water treatment, pool and spa, and indoor air products for independent buying guides. We compare products using manufacturer specifications, certification listings such as NSF/ANSI, UL, AHAM and Energy Star, published third-party test data and verified owner feedback. We do not sell products, and affiliate commissions never decide what we recommend.