Home recirculating hot water heater

[BeyGon]

In our quest for a new place we have seen, in the colder country, homes with recirculating hot water systems, Is this something that can be easily installed in an existing home or from ground up, is it worth the cost?

[porwolf]

I guess it depends how accessible your plumbing is. Can it easily be reached from under the house. Is it a one or two story house. Instead of on-demand-hot-water via recirculating hot water pipes you could think of installing local gas or electric "instant" tank less water heaters near sinks bathtubs and showers . Those are also overall better economically because you don't waste heated water when you don't need it.

[billybek]

Hot water for bathing or hot water for heating?

[Cajundaddy]

Dean,
It's usually pretty simple to add after the fact. The best case is to have your WH near the point of greatest use and run a loop to the furthest point. A small circulation pump can be put on a timer so you have instant hot water in all points during times of high use. Cost varies as it depends on how much copper you need and how accessible the plumbing is. I don't think it will pay for itself in water savings but the convenience factor is great. I recommend it as part of any remodel plan.

[Dueller]

Originally Posted by billybek

Hot water for bathing or hot water for heating?

I have the system in my house. Really saves a lot of money on heating costs. But then again I live in the south.

[porwolf]

Originally Posted by Cajundaddy

Dean,
It's usually pretty simple to add after the fact. The best case is to have your WH near the point of greatest use and run a loop to the furthest point. A small circulation pump can be put on a timer so you have instant hot water in all points during times of high use. Cost varies as it depends on how much copper you need and how accessible the plumbing is. I don't think it will pay for itself in water savings but the convenience factor is great. I recommend it as part of any remodel plan.

A timer is a must for the recirculating water pump if you use copper plumbing. Ask me how I know. When the pump in our building was running 24/7 the relatively new copper plumbing developed pin holes at corners and transitions. After replacing you could see how the copper was eaten up from the inside. A plumber told me the running water causes cavitation in those locations and all it would take is have a timer give the pump a rest of 1-2 hours a day. That made a huge difference, no more leaks.

[Cajundaddy]

Originally Posted by porwolf

A timer is a must for the recirculating water pump if you use copper plumbing. Ask me how I know. When the pump in our building was running 24/7 the relatively new copper plumbing developed pin holes at corners and transitions. After replacing you could see how the copper was eaten up from the inside. A plumber told me the running water causes cavitation in those locations and all it would take is have a timer give the pump a rest of 1-2 hours a day. That made a huge difference, no more leaks.

Somebody forgot to calculate flow rates and/or de-burr their joints. A carefully designed recirc loop will not exceed about 4'/sec. You don't need much pump to accomplish this. 8'/sec will surely begin to erode the copper over time. Having it on a timer just makes sense so you are not recirculating hot water all day and all night.

How it works:
http://www.fiainc.com/documents/6-10%20Domestic%20Hot%20Water%20Recirculation.pdf

[dan88911]

Hope this is helpful.
The Water Heater Payoff - Fine Homebuilding Article

[look 171]

Originally Posted by porwolf

A timer is a must for the recirculating water pump if you use copper plumbing. Ask me how I know. When the pump in our building was running 24/7 the relatively new copper plumbing developed pin holes at corners and transitions. After replacing you could see how the copper was eaten up from the inside. A plumber told me the running water causes cavitation in those locations and all it would take is have a timer give the pump a rest of 1-2 hours a day. That made a huge difference, no more leaks.

Thermo sensing switch that will turn off pump will do the trick. If you have a recirc. pump, most mfg of tankless heater will not warranty their products. my recirc pump turns on about 5-8 seconds every 15 minutes. While I don't get extremely hot water when I turn the lever on my faucet, its hot enough and another 3 -4 second, you will need to remove your hand under the faucet.

[Hugh R]

My water heater was relocated to outside the house when I re-piped 10 years ago, it was in a central closet inside the house with no emergency drain (duh). It takes 30 seconds to get hot water at the shower, I really don't worry about it. Sometimes, if I think about it, I water the indoor plants with the water waiting for it to heat up.

[LakeCleElum]

I have such a pump. Very costly on the electric bill. You circulate hot water, it cools in the pipes, you heat it again. Timer is a must.

[BeyGon]

thanks everyone, I just hadn't seen them before and thought they would be great, I have to wait quite a while for hot water to hit my shower and it isn't that far from the heater in the garage.

[tadink]

As we are living in an ever more water-scarce environment - dumping gallons and gallons of fresh water down the drain waiting for the hot water makes less and less sense.

In CA - our drought is the worst on record now - that 'extra' water isn't extra any longer! And it is going to get worse before it gets better....

The HW recirc loop makes a LOT of sense....ecologically.

td

[JavaBrewer]

In our small 3 bdrm/2ba single level home it takes ~20 seconds to get hot water into the showers (our biggest heated water consumers). Otherwise no issues. Showers are used 4x a day at different times. That's ~80 seconds of water down the drain a day. Water heaters are no longer cheap in SoCal - replacements even need permit/inspection. Crazy. When the time comes I'll look into a couple instant hot systems running electric.

[cabmandone]

If you do some searching you can do a gravity recirculation loop without a pump. That's a win win since you're saving water and not using electricity to recirculate.

[porwolf]

Originally Posted by cabmando

If you do some searching you can do a gravity recirculation loop without a pump. That's a win win since you're saving water and not using electricity to recirculate.

But don't you lose a lot of heat energy by cycling the warm water continuously through the pipes? Unless, of course, they are perfectly insulated. Also the pipe diameter must be quite a bit bigger than the regular 1/2"?

[mikester]

I have a tankless and it takes a bit longer than I prefer for the water to heat up.

The unit is fine - it's just the distance. I'm not sure what I should or could do about it really.

I don't think recirculating is the answer...

More smaller units where I need the hot water might be but then I'd have 'hot water' modules everywhere...

[cabmandone]

Originally Posted by porwolf

But don't you lose a lot of heat energy by cycling the warm water continuously through the pipes? Unless, of course, they are perfectly insulated. Also the pipe diameter must be quite a bit bigger than the regular 1/2"?

I had a friend who used 3/4" cpvc sloped down to a Tee he had put in the drain valve port of the water heater. He had insulated the line with armaflex rubber insulation.

[john70t]

All copper here in Mich.
I wrapped all the basement pipes with foam/metal tape, and kept it off the cold concrete walls.
About $1/ft.

[cabmandone]

Originally Posted by mikester

I have a tankless and it takes a bit longer than I prefer for the water to heat up.

The unit is fine - it's just the distance. I'm not sure what I should or could do about it really.

I don't think recirculating is the answer...

More smaller units where I need the hot water might be but then I'd have 'hot water' modules everywhere...

I installed a small electric tank heater that was plumbed with hot water into the cold so it would get a small amount of cold then blend water until the hot started to feed from the heater in the basement but I had instant hot water in my second floor shower. I guess I had the truest form of a "hot water heater"