Bromine vs Chlorine: Which Sanitizer Is Right for Your Pool

Cost

Chlorine wins on cost, by a wide margin. Liquid chlorine is cheapest per dose; bromine tabs cost 2 to 3 times more per pound and a feeder system needs ongoing tab replacement.

Annual cost for a typical 20,000 gallon outdoor pool: chlorine $300 to $500, bromine $700 to $1200. For a 400 gallon spa: chlorine $80 to $150, bromine $150 to $300.

Smell and water feel

Bromine wins here. The harsh 'pool chemical smell' people associate with chlorine is actually combined chlorine (chloramines). Bromine produces brominated compounds that off-gas less and irritate skin/eyes less for most people. This is why bromine dominates indoor pools and spas where ventilation is limited.

Hot water behavior

Bromine wins for hot water. Above 90 °F, chlorine degrades fast, releases more chloramines, and feels harsher. Bromine stays effective up to 104 °F (the spa max). Most spa manufacturers actually recommend bromine for this reason.

Sun and UV stability

Chlorine wins outdoors. Cyanuric acid (CYA, stabilizer) shields chlorine from UV. Bromine has no equivalent — direct sun burns through bromine in hours. An uncovered outdoor bromine pool needs a high feeder rate and constant attention.

If you have a covered or shaded outdoor pool, bromine can work. If your pool sits in direct sun all day, chlorine is far more practical.

pH stability

Roughly equal. Both sanitizers cause pH drift over time (chlorine pulls pH up; bromine pushes pH slightly down). Both require routine pH adjustments. Bromine is slightly more forgiving at the higher end of the pH range (7.6 to 7.8) because its sanitizing effectiveness drops less with pH than chlorine does.

Shock and recovery

Chlorine pools shock with Cal-Hypo or similar at 2 to 3 lb per 10,000 gallons. Bromine pools shock with non-chlorine shock (MPS) at 1 lb per 10,000 gallons. Both restore the sanitizer to active form, but MPS does not add chlorine to the water (so you can use the pool sooner after shock).

Skin and eye comfort

Subjective but consistent: most people find bromine gentler on skin and eyes, especially in hot water. Anyone with sensitive skin, eczema, or chlorine allergies often does better in a bromine pool.

On the other hand, bromine can dry hair more (the chemical bonds to hair protein). Rinse hair after every swim if you have color-treated hair in a bromine pool.

When chlorine wins

Pick chlorine if you have a typical outdoor in-ground pool, want lowest cost, do not have a strong reaction to chloramines, and use the pool in regular daylight. This describes 80%+ of residential pools in the US.

When bromine wins

Pick bromine if you have a spa or hot tub, an indoor pool, an outdoor pool that is usually covered, anyone in the household has sensitive skin or chlorine sensitivity, or you simply hate the chlorine smell. Bromine costs more but the quality-of-life difference is real for many owners.

Can I switch?

Yes, but allow a transition. Bromine and chlorine coexist in water for a while because residual bromide stays in the pool for weeks after you stop adding bromine tabs. The fastest way to switch sanitizers is partial drain + refill, then start with the new sanitizer from scratch.