Gas Hot Water Tank

I just had a new hot water tank installed. I have a cold water pipe/valve coming out out of my wall at the top of the hot water tank and I have a cold water pipe/valve coming out of my floor.
My old hot water tank had both of these hooked into it. One at the top and one at the bottom. I also would instantly have hot water at any faucet in the house.
My plumber did not hook up the bottom cold water and said it was not necessary. He turned off the bottom valve.
Now it takes 5-10 minutes to get warm water in all faucets in my house.
I feel like there is so much water waste waiting for hot water and something isn’t right. Could it be the bottom connection?

Pictures would help but it sounds like you are on the right track:

Sounds like a lazy ass plumber didn’t want to bother dealing with a recirculating pump!


It sounds like the recirculation system was not hooked up to the new water heater. The system maintains warm water at the plumbing fixtures by using a pump to cycle warm water through the plumbing loop, even when the fixtures are not in use. This type of system can save water, but results in higher eneregy costs due to having to constantly reheat water that has cooled off in the loop. It’s a pick your poison type of deal.

Example of Recirculating Pump Traditional Grundfos, Laing, Taco

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How many sqft is your house?

Pick your poison as far as waste goes - Current setup you waste water, old setup with the pump you waste energy as the water in the loop is cooling off as it’s being circulated and you aren’t using it. I get the hassle and inconvenience but I don’t know that “waste” is a reason to hookup the pump.

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  1. IMO, as long as the water is moving into and out of the tank, there is very little heat loss from the water… just the loss of the energy to power the pump, and to reheat the small amount of cooler water returned back to the tank.

  2. An experienced plumber will simply install a timer for the pump so the pump doesn’t operate at traditional peak times, like overnight. Could also install switch at each primary fixture to turn the pump ‘on’ a few seconds prior to needing use. Most decent pumps work fast. Don’t need 5 minutes run time to get hot water to the farthest fixture.

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I had never really done a deep dive on this and was more just basing my opinion on the theory that some energy waste was occurring. Here’s an article from a guy that says his pump is using an extra 200 gallons of propane/year. That seems excessive but possible I suppose.

From the article: I estimated the energy waste for recirculation by measuring the amount of energy my gas water heater uses with and without the recirculation loop enabled. With the recirculation system on, the gas burner comes on every 1.25 hours for 5.1 minutes. With the recirculation system off, the burner comes on every 5 hours for 5.1 minutes. All of these measurements were taken over the night period when no hot water was being used. If you go through the math on this (see below), it comes out to 200 gallons of extra propane wasted per year to support the recirculation system.

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Matt: it’s an energy loss for sure, but complicated. In winter it’s just an alternative heating source. In summer it’s increasing A/C load.

The intermediate solution – between a 24/7 pump and nothing – is “faster” hot water. Either flow or button activated recirculation, with or without a dedicated return pipe. See a link below.

For the OP: is your home two story and the WH in the basement? Or level with the WH somewhat lower than the home? It’s possible you had a thermosiphon spoiled either by the inlet change or by a new energy saving check valve built into more recent heaters:

A thermosiphon works because hot water rises, cold water sinks. I’ve removed nearly as many pumps as I’ve installed, because the plumbers did not understand the physics of this.




Isn’t this assuming pipes are run through living space? Definitely not always the case in my area. I hadn’t even really considered that aspect. I was more thinking of the excess usage of fuel to heat the water. That’s mainly what the article I referenced was pointing out as well. I’d have to think heat load, A/C load and electricity to run the pump are pretty minor in comparison to the increased cycling of the water heater.

“The scientific law of conservation of energy states that energy can neither be created nor destroyed - only converted from one form of energy to another.

So you have to consider where each unit of energy is converted, and what it converts to. In my area most pipes are inside, but whatever – we can still do the math.

The outside pipe loses are lost to the outside air, easy.

The inside pipes heat the interior, which in an A/C climate is then pumped back outside. If the heater is resistance and the A/C is a heat pump the coefficient of performance will be between say 3 and 5. For every unit of heat produced by the water heater, 1/3 to 1/5 is lost re-exporting the heat to the outside.

In a heating climate during heating season: there’s no loss. It’s just an additional heat source. You then look at the relative efficiency of the heaters. If the central has an AFUE of 98%, for example, that’s way better than any normal gas water heater. The energy transfer gives you a net positive gain – the pipe losses are a net benefit.

Just go back to energy can neither be created nor destroyed - only converted from one form of energy to another. and figure out the flows including flue and tank standby losses. Standby losses are particularly high for tank gas heaters regardless of insulation.

One of my frustrating repeat experiences is trying to convince HVAC installers to leave off all their freaking foil insulation, from HVAC units and pipes installed entirely within conditioned space. All that crap is completely and totally useless. But teaching basic thermodynamics (e.g. energy can neither be created nor destroyed - only converted from one form of energy to another. ) does not often seem to work with tradespeople.

I was able to help get that changed at the California State level: the Title 24 regulations no longer require the useless insulation.

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