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Expansion Tank

I have a tankless water heater. Someone recommended that I remove the expansion tank because it increases the energy usage. I don't know if this removal was the cause but the water heater doesn't seem to function properly.

It takes about 5 minutes of turning on the faucet for the hot water to flow. After about 5 minutes, the hot water will run out and I have to wait another 5 minutes for additional how water.

Is this normal?


  • Lance
    Lance Member Posts: 271
    Expansion tank or is it another problem?

    Expansion tanks are a critical component to prevent damage and high pressures created from expansion of a liquid in a closed environment. While tankless heaters minimize this effect, it is the manufacture specs that must be followed. We are warranty tech reps for water heater companies and often disallow warranties or fail commercial startups when expansion tanks are not present. Many times I have seen tankless heaters undersized, because the specs weren't really understood, or the btu input was not present or changed to accommodate a large enough heater. Just to get 3 GPM flow out of a tankless requires at least 150,000 BTUH input. Also some heaters have flow restrictors designed in them to try and maintain a temp set point when flow rate is exceeds it set point. Or the heater could be malfunctioning. Good luck.
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