I live in an apartment complex and each apartment has its own hot water heater. If I turn my kitchen sink on first, I get no hot water at all until another faucet in the bathroom is turned on. Then when the bathroom runs hot the kitchen immediately goes to hot. Vice Versa for the bathroom sink first and then the kitchen sink.

The property manager changed the mixing valve and still no results.
Any help would be greatly appreciated.

  • 6
    Do you have a tankless water heater? Those often have minimum flow rates. Couple that with new mandatory low-flow faucet nozzles and you get this problem.
    – Matthew
    Aug 30, 2018 at 3:16
  • Matthew: Thank you for your comment. I will share this with my property manager to see what he thinks of this.
    – Harriet
    Aug 30, 2018 at 3:43

2 Answers 2


I would guess that you have a tankless water heater with a minimum flow rate.

If your faucets also have low-flow nozzles (now required by law in California) it's possible that a single sink wouldn't trigger tankless water heater to turn on.


Check the aerator screens on all your faucets to see if they are plugged. This would restrict the flow and could put it below the minimum for a tankless heater.

If you have a tub, these are not usually fitted with a flow restrictor and so I would assume that the tub on full would give hot water. But shower heads are usually fitted with a flow restrictor and so I would assume that the shower might not deliver hot water. Does it?

Check the instructions for the tankless heater to see if there is an adjustment which would lower the minimum flow required for it to turn on. Usually the kitchen faucet is not as low flow as a lavatory.

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