Every dose, every filter size, every cover measurement.

How this site works

We have not tested these products

That sentence is the first thing on this site rather than the last, because it is the thing every other site in this category gets wrong. The field is full of roundups claiming rigorous testing of twenty hot tub covers, written by people whose stated qualification is a horticulture certificate or teaching literature. We do not have a lab, we do not own these products, and we are not going to pretend otherwise.

What we do instead is reproducible, which a test lab’s results are not. We compile the manufacturer’s published specifications from the label, the spec sheet and the manual. We check every water-chemistry number against the CDC’s published guidance rather than against another blog quoting it. We do the arithmetic — dose per gallon, cost per treatment, cost per season — and we show it, so you can redo it. And where owners consistently report something, we say it is anecdotal, because it is.

The test of any claim on this site is simple: if you asked us how we know, could we answer with a document, a standard or a calculation you could repeat yourself? Where the honest answer is that we do not know, the page says we do not know. The full method is published here, and every commercial page links to it.

We are funded by affiliate commission, which we disclose above the first link on every page that carries one, and again in the footer. Where the better buy is a retailer we earn nothing from — custom-fit spa covers, for one — we say so and link them anyway. How we make money, in full.