Recirculating pump for instant hot water.

Interesting idea. Never heard of this pump, but it certainly can solve a problem. At worst, the thing can have a switch, and connected when going to use the shower. Or a timer. Push the button, and have an hour of instant hot water.

You might replace the thermo-valve with a sensor that would both switch a valve and disconnect the pump. Or the pump could be installed at the end of the run, perhaps, no valve.

In my case, the pump would need to put some pressure, because I have a flash or instant gas heater. It fires when there is hot water flow, by detecting a pressure drop, I guess.

Yes, I have seen the idea of a button at the sink, it does save the wasted water but not the time waiting for hot water. It would probably be a longer wait because I suspect the pump has a lower flow rate than the normal outlet water flow. It seems like the pump could have a pressure sensor on it to know when the thermovalve shut, but sense it is not a displacement type pump, I don't have any idea if there is any or what the differential pressure is. Mikek

I had these pump before. So, a few observations: it only save money for gas water heater. Otherwise, it would be better to have electric heater closer to the faucel. The pump tends to lock up if not in use for long period of time. Suggestion is to run at least a few minutes per day.

Regarding cold water pipe recirculation, you would have to be careful about drinking from tap water. Hot water have more bacteria. You don't want to mix up hot and cold pipes.

I mentioned that, open endedly in my previous post because I don't know what the pressures would be. You have a pump that is already at 50 psi at the input and it may have slight increase to make the water flow, but I don't think is is much pressure

Ya, I'm already not to happy the the thermal valve works at 90*F so the water is already not hot. I think that is a tradeoff so as to reduce the cost of the wasted heat lost in the pipes.

I understand the idea, just not sure about a point of use water heater and a circulation pump.

Eight cents per shower doesn't sound like a big problem to be solved. A second shower, or showering with a friend, is free.

Just run them in series, local electric water heater with a small tank, fed from the long slow pipe from the main water heater.

We keep a bucket in the shower and run the water into that until it gets hot. We water plants from the bucket. That takes maybe 2 gallons.

Why would it only save money for a gas water heater? Second, I'm not sure it ever saves any money, as I think the extra cost to heat water that just cools in the pipe many times per day is higher that the money saved on less water wasted down the drain. Otherwise, it would be better to have electric heater closer to the faucet. The pump tends to lock up if not in use for long period of time. Suggestion is to run at least a few minutes per day.

Hmm, I have not seen any discussion about bacteria on the many pages of info I have read. This is the way these pumps are used, generally only on new installations is a separate return pipe used. Years ago we built a house with the water heater in the basement, I did add a return line and the whole thing was gravity fed so no pump needed, it worked very well. Here is a somewhat typical pump although this has the extra bells and whistles like a timer and the thermal valve.

I considered using waste water to preheat the cold water coming into the water heater. There are gadgets to do that, and our incoming water is always cold. But it would be a hassle with decades to pay back.

It's not a big problem, and it all started with just wanting instant hot water at the kitchen sink, finding not enough room under the sink and then reading about recirculation pumps and the thermal valve then finding they are often installed at the farthest sink. Now I've expended my thinking to the whole house instead of just the kitchen sink. Although I may just drop back to the kitchen sink.

Ya, that's something my wife would do, but I'm not about to fill a bucket until the water is warm then set the bucket out into the bathroom and take my shower, then worry about watering the plants. But, I'm not in CA. either, with all your states rules. Mikek

I need it to have the same flow of water as the tap. If the flow is too small, the boiler doesn't fire. If it is different, the temperature differs from the normal status. For example, if the flow is small, but enough to trigger the boiler, say half of the normal tap flow, I would get double the temperature for a while.

The button idea is to have the system active for a time, say one hour, then it goes off. My pipes are not insulated, so I would waste too much having the system waiting and ready the whole day.

Recirculation will waste heat. Some of the heat from hot pipes will go outdoors and some will diffuse indoors, good in winter but bad in summer.

My wife is the plant person here. All I do is run the shower into the bucket. I was waiting around anyhow.

No state rules apply to the bucket.

Personally, I think this is not a good idea. It doesn't solve the problem of the hot water cooling in the pipe, in terms of the cost to heat it. In fact, it ramps up that cost by assuring there is constantly hot water that is losing heat.

In Puerto Rico, they actually seldom bother with hot water at sinks. You don't really need 130°F water to wash your hands. Some places use an instant hot water heater for the whole house. Those tend to not work so well, as the water cools significantly by the time it reaches the sink or shower. This may be because the pipes are run in the concrete walls or floors, which wicks away heat more rapidly than the air space in lumber and dryrock construction.

But they also use instant heaters at the point of use. These work well, if sized properly. 120V tends to be a bit less heat than you might like, but is generally good enough. One place had an instant hot water heater for the house, using gas. It seemed to cut in and out, with the water temperature going hot, then cold, every couple of minutes. Not much fun in the shower!

It is not uncommon for larger houses to have two hot water heaters, one for the main level, and one for upstairs. I have estimated my 30 year old hot water heater uses about 3 kWh per day, when no water is used. I get this from the whole house electrical use when no one is home. The normal level runs 0.384 kWh (reported units are multiples of 128 Wh/hr) and spikes up to around 0.896 kWh per hour once, every 4 hours. So that's about $0.35 per day, or $2.50 a week.

So how much would it cost to keep the water hot, in 50 feet of uninsulated copper pipe? I bet it doubles the cost of the hot water heater idle power. I think I'd opt for good quality instant heaters, or install a second hot water heater (it can be a smaller unit and can be in the attic).

Ah. That's because water can not flow back to the municipal pipes.

There is another method: the hot water tank has a portion of air at the top of the tank. And, the tank itself has a little relief valve at the bottom. Now I clearly see why.

Curio history.

At a flat owned by a friend of mine they had such a hot water tank. The floor was number 7, I think. The municipal network only grants that the water reaches the ground level, the building has a tank and a pump to push the water up. A pressure group, they call that here. But these pumps don't create a constant pressure, but oscillating between a high and low levels, constantly. This means that a little bit of water was entering my friends flat, and exiting, oscillating in an out, up to a few times per minute (say four). And, the flat has a water meter, that doesn't count the water going out.

Result was the flat got an invoice for many thousand litres a month, a significant number of euros.

The called a profesional plumber, who took a long time to find "the leak". Then he installed a one way valve.

...

I have that, it's very common here. The temperature is constant, as long as you don't touch the hot water tap and the water flow is constant.

There are two types: cheap, there is a constant gas flow, so the less water flow, the hotter it is. Expensive, there is an electronic regulator changing the gas flow trying to keep the temperature constant.

Oh, those I have seen can certainly be used often. Mine has a little lever I can move with my finger and see water come out.

I guess that plumber now knows ;-)

That kind of pump (design from 1980) has a reservoir, typically a metal sphere with an air filled rubber balloon inside. A pressure switch connects the pump when pressure is low, disconnect when high. Thus, the pressure oscillates.

I think there is a design that couples a pump and an inverter, running continuously, that keeps a constant pressure. But runs non stop. If the water flow will be constant, it is a good alternative.

OK, that seems reasonable, but I question the company. All I find on their site is a rebuilt pump with all the accessories, a rebuilt pump with only the temp sensor included and two remote controls, white and brown. I've been over the site and can't find any new pumps with accessories. I expect a time will come when Grundfos/Watts comes out with a remote system for pump control, but they seem pretty late to implement it. Mikek

It senses the temperature at the farthest sink and turns the pump on or off. The others have a thermal valve that closes to stop recirculation, but it does not shut off the pump. This could be done with a temp sensor at the sink and wiring or an RF link back to the magic black box that controls operation of the pump.

Uhm, not sure you explained that right, but yes, there is a way to control the operation of the pump by the temperature of the water at the sink.

I'm a little suspicious of my kitchen sink, it is only 6-1/2 ft from the water heater, but it takes 0.87 gallons to get hot water, So, I'm not sure water the pipe route is.

OTOH, those devices could just be electrically operated

Not sure I understand what you are trying to do, but if I went with an electrically operated valve, it would go between the hot and cold at the farthest sink, in that position it would not effect water flow when no electricity is present. Also, I would expect a valve to be normally closed so without power there would be no mixing of hot and cold water.

The price is right, the amperage is not right for most home wiring, the safety and quality have to be questioned. But at $2.87 with free shipping for a 3000 watt heater... :-)

I don't think there is any difference. But you would need a temperature sensor and magic box to control the pump and is you have a thermal valve it would not be used. I am curious how the pump at the water heater affects the flow rate. I have not read any complaints about reduced flow rate, so I suspet it is minimal.

Same here, on a slab. Florida.

Is that for flood protection?

I just lift the cover over my water meter and shut it off. I have a buddy that got a whopping water bill one month, but didn't see any water in his yard. He end up poking around with a rod until he found a soft spot , dug it up and found the break.

Other sellers have it at $60, must be Red isn't selling, so it is discounted! :-)

If you have the Kitchen Aid mixer, take it apart and regrease it, We did that 10 years ago and passed it on to our daughter.

:-)