I plan to install an under-counter hot water dispenser and want to pre-filter the water. I found this product that already includes a pre-filter, but the cartridges appear to be proprietary and overpriced.

I'm wondering if it's possible to install a generic inline pre-filter in front of a standard hot water dispenser. Specifically, I'd like a filter that removes chlorine, or at least its smell and taste. Could there be problems with insufficient water pressure or other problems I'm not aware of?


You want to get an activated carbon filter (see this answer for an overview of how it works).

You'll probably want to look at a standard 10" filter housing and a matching carbon filter, both of which are readily available online and in retail everywhere, including the big box stores.

filter housing

This can go under your sink or elsewhere upstream. There are clear models available, though these are really only useful for a sediment filter, and even then monitoring the pressure drop across the filter(s) is a better way.

Be sure to install an upstream shut-off nearby (if there's not one already) so you can turn it off to change the filter. And pro-tip: if you're installing under the sink or other confined location, dry fit it and ensure you'll have enough room to replace the cartridge.

activated carbon filter block

For activated carbon, all you can really do is monitor for taste, and/or change it on a schedule (off the top of my head, at least every 6 months seems reasonable, but check what the manufacturer recommends). The filters are actually rated based on flow rate and the total volume they can handle.

You can also put the filter upstream of more than just the hot water dispenser (eg, include your kitchen sink cold water as well), and depending on your plumbing and space this might be easier or make more sense. Just be aware of the flow rate (gpm) rating, and total volume. I'd guess for most uses serving the kitchen cold tap only, a 10" filter would still be fine for this but you do have the option to go to 20" if you need more volume/flow and have the space.

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This worked out beautifully. I connected this filter. I later replaced the "advanced" filter with a compatible 3m standard filter because the flow rate on the standard 3m one is even better than the advanced.:

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in front of my cold water faucet output as well as this instant hot water dispenser:

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I get more than enough pressure to support the hot water dispenser, and the drop in pressure to the faucet for cold water is perceptible but still plenty high enough that unless you were doing a side-by-side comparison, you'd never notice or complain. The sink sprayer works just fine with the slightly reduced pressure as well.

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