Water Urns and Pump Pots on Yom Tov

From kosherquest.org/water-urns-pump-pots

The cRc is in the process of researching whether one may add cold water to hot water urns and pump pots on Yom Tov. A number of these devices claim that it is permitted to add water, and thus far, our testing has shown that – in certain devices – this claim is not accurate. We recommend that cold water should not be added to any urn or pump pot on Yom Tov, absent a contrary ruling from one’s local Halachic Authority.