Good questions.
Clear evidence.

What was measured

Free residual chlorine and combined residual chlorine (chloramine) in tap water, before and after 100 L passed through the filter, in an independent third-party laboratory using the Korean test method for water purifiers. Both were not detected after filtering. An earlier independent test measured free chlorine at shower temperature, also to non-detectable. Our customer-facing claim is 99.9% reduction of chlorine and chloramine.

What not detected means

The remaining concentration was below the test’s detection threshold. It does not mean that every possible contaminant was removed, or that all water conditions produce an identical result.

Keep the scope clear

These results are separate from the NSF/ANSI 42 certification of the PP sediment filter. They do not establish NSF certification of the complete showerhead or a comparative result against another brand. The tested sample was the Showerhand filter, which uses the same Vitamin C media as the Showerhead.

Source: Second Shower independent third-party laboratory tests. Free and combined residual chlorine (chloramine) after 100 L, 2026; free chlorine at shower temperature in an earlier test. Individual water conditions and use vary.

Study design

An independent clinical human-application study of 22 women using The Second Showerhead/Showerhand for two weeks. Facial skin measurements were compared with baseline. There was no control group.

Measured outcomes

At two weeks: hydration +26.71%, excess facial oil −69.37%, pores −18.54%, dead-skin/keratin −11.29%, and glow +10.93%. Reported statistical significance: P<0.05.

Reading the first-week data

The approved first-week oil result is a range, −24–27%. The chart shows 24% in yellow with the remaining range in grey. A first-week dead-skin value is not reported and is not plotted as zero.

What the design can tell us

This study records changes during use. Without a control group, it cannot isolate the product’s contribution from other influences or establish a result for every skin type.

Tolerance

No adverse reactions were observed in the dermatologist evaluation of this study. Reported compliance was 98.4%. This does not rule out an individual sensitivity.

Source: Second Shower clinical study summary. 22 women, 2 weeks, P<0.05 for the reported two-week instrument outcomes. No control group. Individual results vary.

Same study, different evidence

Participants rated statements about their experience from 1 to 5. The chart reports the percentage who selected 4 or 5.

95% felt less skin tightness; 82% felt smoother, more hydrated skin; 82% felt healthier, shinier hair. Ease of installation received a mean rating of 4.9 out of 5.

Separate six-week user study

In a separate internal six-week user study, 95% reported less skin dryness, 91% softer hair and 88% clearer skin. These are self-reported observations, not the two-week clinical measurements. We do not combine the two datasets.

Source: Second Shower clinical-study perception survey. Same 22-woman, two-week study. Self-reported experience; individual results vary.

PP sediment filter

We use an NSF/ANSI 42 certified filter. This applies to the micron PP sediment filter component, not the complete showerhead. Chlorine performance is attributed separately to independent laboratory testing.

Water efficiency

The California-compliant versions are rated at 1.8 GPM. Documented measured flow is 1.54 GPM for Showerhead and 1.69 GPM for Showerhand. Standard 2.5 GPM versions are also offered; check the selected product version.

Read about the standards

NSF’s guide to water-treatment standards explains the different scopes. This general guide is not a product listing.

Source: Second Shower component-certification and water-efficiency documentation summaries. Flow figures apply to the California-compliant versions.