Your personal
pool coach

What does Pool Buddy cost?

Pool Buddy is completely free and ad-free – there is no premium tier, no in-app purchases and no hidden costs. You don’t need a user account or an App Store installation: the app runs directly in your browser at pool-buddy.de and can be installed like a normal app via “Add to Home Screen” whenever you want. All pool data – measurements, pool volume, chemical inventory – stays exclusively in your device’s own storage (localStorage) and is never transmitted to any server. There are no user-tracking profiles, no mandatory newsletter and no advertising overlays. The public information pages use a cookie-free, anonymous visitor count (Umami); it is not loaded on the app screens themselves. The project is developed as a private side project by the operator based in Roßtal, Bavaria, and is financed without sponsors or affiliate links. If you would like to support ongoing development voluntarily, you can buy a coffee via ko-fi.com/PoolBuddy – otherwise a recommendation to other pool owners or a bug/feature report via the contact page helps just as much.

Which pH value is ideal in a pool?

The ideal pH value for a private pool sits between 7.0 and 7.4 – just inside the slightly acidic range but close to neutral. This narrow window is where free chlorine works most effectively: above pH 7.6 chlorine can be up to 50 percent weaker, below pH 6.8 it can attack metal filter parts and irritate skin and eyes. If the reading is too low you dose a pH increaser (typically sodium carbonate); if it is too high, a pH decreaser (usually sodium bisulfate). Run the filter pump for at least two hours after dosing so the product distributes evenly, then measure again – ideally with an electronic photometer or fresh test strips (strips older than 12 months often give false readings). Pool Buddy shows you the exact dose in grams or millilitres for your specific pool volume with every measurement.

How much chlorine belongs in pool water?

In a private swimming pool, 1 to 3 ppm (mg/l) free chlorine is the established target range – recommended by DIN 19643 for public pools and adopted as a good balance between disinfection strength and skin tolerance in home pools. Below 1 ppm, chlorine can no longer reliably kill bacteria and algae; above 3 ppm the risk of eye, mucous membrane and swimwear irritation rises. Only free chlorine actually disinfects – combined chlorine (chloramines) is the strong “indoor-pool smell” and a sign of too much organic load. At water temperatures above 28 °C, strong sunlight or many bathers, chlorine is consumed much faster; measure daily and, if needed, set cyanuric acid (chlorine stabiliser) to 20–40 ppm so UV light does not break the chlorine down. Pool Buddy warns automatically when your reading is outside the target window and calculates the exact dose for your pool volume.

What should I do if the pool water is green?

Green pool water almost always means an algae bloom – triggered by too little chlorine, an elevated pH or high heat input. The proven recovery order: First, coarse cleaning – brush walls, floor and waterline thoroughly with a pool brush; vacuum any visible algae from the floor. Second, adjust the pH to 7.0–7.4 because chlorine works most strongly in this range. Third, perform a shock chlorination: 10–20 g of chlorine granulate per cubic metre of water; calculate the exact amount with the dosing calculator. Fourth, run the filter for 24 hours without interruption; backwash mid-cycle if it clogs. Fifth, measure again the next day: when the water is clear and free chlorine is below 3 ppm, the pool is safe to use again. For stubborn algae, add an algaecide according to the manufacturer’s instructions. Pool Buddy walks you through diagnosis step by step and reminds you when the follow-up measurement is due.

How often should I measure water values?

For a normally used garden pool, two measurements per week for pH and free chlorine are enough – for example Monday and Thursday. Measure daily when water temperatures rise above 28 °C, after heavy rain (dilutes chlorine and shifts pH), after thunderstorms (lightning inputs can break down chlorine), after pool parties with many bathers or right after a shock chlorination. Additionally once a month: alkalinity (target 80–120 ppm), total hardness and – if used – cyanuric acid. Alkalinity acts as a buffer against pH swings; if it is too low, the pH will jump after every dose. Take the sample at least 30 cm below the surface and 30 cm from the pool wall, ideally in the morning before strong sunlight. Pool Buddy reminds you on time, logs every measurement with a timestamp and plots trends across the season.

Does Pool Buddy also work offline?

Yes – fully. Pool Buddy is a Progressive Web App (PWA) and uses a service worker that caches all resources (HTML, JavaScript, icons, translations) locally on your device the first time it is loaded. From then on the app works 100 percent without an internet connection: enter water values, run diagnostics, calculate doses, review your history – everything runs from the browser cache. This is especially handy at a garden pool where Wi-Fi is weak, or on holiday without a stable network. You can install the app via “Add to Home Screen” (iOS: Safari share menu; Android: Chrome menu “Install app”) like a normal app, complete with an app icon and full-screen mode without the browser bar. Updates are pulled automatically once your device is online again. The only exception: the optional weather hints briefly need internet to load a fresh forecast for your postcode – they then continue to work from cache offline too.