Viqua PRO20
#2 in Over 12 GPMFull review
The certified pick for a large home or a small business on a private well. It costs a lot, but the dose is measured and certified.
Amazon $3,840$3,840
The Viqua PRO20 is the better UV water purifier overall, rated 3.6 to 2.6. The Viqua PRO20 leads on certification. The HQUA TWS-24S costs $3,340.01 less ($499.99 vs $3,840).
HQUA TWS-24S
#6 in Over 12 GPMFull review
A cheap high flow unit for a large home that wants a UV backstop in a small space. The rating is unverified, so size it generously.
Amazon $499.99$499.99
Prices were last checked November 2, 2026 and are subject to change; the price and availability shown by the retailer at the time of purchase apply.
Which should you buy?
- Choose the Viqua PRO20 for certification (NSF/ANSI 55 Class A vs not NSF/ANSI 55 certified, and no UV dose published).
Scores side by side
Each factor is scored 0-100 against the same fixed reference points for every over 12 GPM UV water purifier; a clear win is highlighted. How we rank explains each one.
| Factor weight | Viqua PRO20 | HQUA TWS-24S |
|---|---|---|
| Overall rating | 3.6/5 | 2.6/5 |
| Value 25% | 16 $192 per GPM ($3,840, 20 GPM at 40 mJ/cm²) | 65 $52.08 per GPM ($499.99, 9.6 GPM at 40 mJ/cm², from 24 GPM at an unstated dose taken as 16) |
| Certification 20% | 100 NSF/ANSI 55 Class A | 0 not NSF/ANSI 55 certified, and no UV dose published |
| Monitoring 20% | 100 UV intensity sensor, lamp failure alarm, shutoff valve, lamp change countdown | 50 monitoring not published (neutral score used) |
| Lamp life 10% | 44 18,000 hour mercury lamp | 50 lamp life not published (neutral score used) |
| Warranty 25% | 44 5-year warranty | 0 warranty not published, scored as none |
Specifications
| Viqua PRO20 | HQUA TWS-24S | |
|---|---|---|
| Disinfection | ||
| Rated flow | 20 GPM at 40 mJ/cm² | 24 GPM |
| NSF/ANSI 55 | Class A | No |
| Lamp | Mercury | Mercury |
| Lamp power | 140 W | 80 W |
| Lamp life | 18,000 hours | - |
| Monitoring | ||
| UV intensity sensor | Yes | - |
| Lamp failure alarm | Yes | - |
| Lamp change countdown | Yes | - |
| Shutoff valve | Yes | - |
| Build | ||
| Chamber | 316L stainless steel | 304 stainless steel |
| Ports | 1.2 in | 1 in |
| Maximum pressure | 125 psi | - |
| Voltage | 120 V | 120 V |
| Warranty | 5 years | - |