How Do I Tell If My UV Bulb Is 2-Prong or 4-Prong Before I Reorder?

The single most common UV reorder mistake is the wrong pin count, ordering a 4-prong (4-pin) lamp when the system actually takes a 2-prong (2-pin), or the reverse. The fix is simple: identify your existing lamp before you order, do not guess from memory. Match the pin count, then the overall length and any markings printed on the old lamp. If you would rather not select it yourself, give our team your system model, original order number, and clear photos of the lamp base, full lamp, and printed markings.

Current Crystal Quest catalog mapping:

In the current catalog, suffix A is the 2-prong version and suffix B is the 4-prong version. Still verify the physical lamp visually, because the catalog contains multiple lengths and system families.

What Identifies a UV Lamp

A few things to know:

• UV lamps are identified by their base type and pin count (commonly 2-pin or 4-pin), plus their length and wattage class. The pin count is what most often gets mixed up, so confirm it first.
• The lamp and the protective quartz sleeve around it are different parts. A lamp that looks dark or has reached its service life still sits inside a clear quartz sleeve; do not confuse the two when ordering.
• UV lamps should be replaced every 12 months to keep disinfection effective, so it is worth identifying yours correctly once and noting it for next time.

Safety Before You Start

Always disconnect power before opening a UV unit or handling the lamp. Do not look at an operating UV lamp; the light can damage eyes and skin.

• Handle the lamp and the quartz sleeve gently. Both are glass and can break; dispose of an old lamp responsibly, as UV lamps may contain materials that require proper disposal per local rules.
• Do not run a UV system with a missing or unseated lamp expecting it to disinfect. If the lamp is not the correct type and properly seated, the water is not being treated as intended.

How to Identify Your UV Lamp

1. Power down and unplug the UV unit before touching the lamp. UV systems run on line voltage and the lamp produces UV light that is harmful to skin and eyes, so never operate the unit with the lamp exposed.
2. Let the lamp cool, then remove it from the chamber per your unit's instructions. Handle it by the base or with a clean cloth; skin oils can shorten lamp life.
3. Look at the base (the plug-in end) and count the pins. Two pins means a 2-prong (2-pin) lamp; four pins means a 4-prong (4-pin) lamp. If both ends have pins, note that as well.
4. Measure the overall length of the lamp end to end, and write down any model number, wattage, or markings printed on the lamp. Take clear photos of the base and pins, the full lamp next to the measurement, and the printed markings.
5. Match all of it (pin count, base type, length, and any printed markings) to your replacement. If anything is ambiguous, do not assume; confirm with us.
6. When installing the new lamp, slide it back into the quartz sleeve and seat the base fully. If the sleeve is cloudy or scaled, clean or replace it per your unit's instructions while you have the chamber open.

Quick Summary

• Count the pins on the base of your old lamp: two pins is a 2-prong (2-pin) lamp, four pins is a 4-prong (4-pin) lamp
• Match pin count, base type, overall length, and any printed markings before you order; do not guess from memory
• Always disconnect power and let the lamp cool before handling it
• The lamp and the clear quartz sleeve are different parts; do not confuse the two when ordering
• UV lamps are typically replaced about every 12 months to keep disinfection effective

Need Help Identifying Your UV Lamp?

Reach out to our team if:

• You are unsure of the pin count or base type, or your lamp's markings are worn off.
• You received a UV lamp that does not match (for example, a 4-prong arrived but your system takes a 2-prong). We will send the correct lamp; keep any O-rings that came with it unless we tell you otherwise.
• You are not sure whether you need a new lamp, a new quartz sleeve, or both.

Give us your system model, original order number, and the clear photos described above, and we will confirm the exact UV lamp and sleeve for your unit.