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Thread: Long run to kitchen hot 4 min to hot water!

  1. #1
    DIY Junior Member foamy's Avatar
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    Default Long run to kitchen hot 4 min to hot water!

    Hello out there!
    I have searched the threads and found somewhat similar problems but none with a concrete slab. My house has pipes running through a concrete slab and it's a 65 foot run from the water heater in the garage to the kitchen sink. It's about 4 minutes from turn on to hot water in the kitchen. I understand the heat loss due to the thermal mass of concrete. However, is there a solution? Any suggestions would be kindly appreciated.

    Thanks

  2. #2
    Retired Defense Industry Engineer jadnashua's Avatar
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    If you don't want to relocate the pipes, and it's unlikely you'll be able to insulate them, the only other choice is to pick up a hot water recirculation system. Lots of companies make them. Since you don't have a dedicated return line, the retrofit units utilize the cold line as the return, so that water line will get somewhat warm (there's a thermostatically controlled valve or control to prevent it from getting the full temp of the hot line. I have one made by RedyTemp, but there are lots of others that would work, and work well. if you search the forum on recirculation, you'll find lots of info on brands and issues. You can set the thing up on a timer, a demand switch (that only runs when you press the button for a short time), an occupancy sensor, or constantly.
    Jim DeBruycker
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    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Senior Member Smooky's Avatar
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    You could take the aerator out of the spout. This is the thing that screws off at the end of the faucet. It restricts the amount of water that flows out, taking longer for the hot water to get there. Then more water would flow through the faucet faster so instead of 4 minutes it might be more like 1 minute. If you do that, just take out the plastic part that restricts the flow but leave the screen. This way you will get plenty of volume, without making a distorted flow......Another option would be to put a small water heater under the sink. It would be plumbed into the hot line at the sink. The tank would not need a large volume because of the main hot water heater would be feeding it.....I do not like the recirculating system that sends warm water back to the cold line. The problem with this is you can not get cold water or now you have to wait for cold water too.

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    Plumber jimbo's Avatar
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    The problem is that you have a certain number of gallons of cooled off water in the hot pipe, and it must be forced out before the heated water arrives from the tank. Your long pipe run means a long wait.

    Smooky pretty well summed up the two alternatives, and the drawbacks of each. A 2 gallon point of use water heater is probably easier to install than even a basic recirc system, EXCEPT that it does have a relief valve which has to be piped to outside the building, by most codes.

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    DIY Junior Member foamy's Avatar
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    Hey Jimbo,
    Thanks for the reply as well as thanks Jadnashua and Smooky as well! As smooky stated I am not looking forward to waiting for cold water either. It seems like a separate system for the kitchen is the only option. How would a 2 gal point of use system work? Would it just be 2 gals of instant hot water until the cold water left in the hot water line was pushed out? And if so, where would the cold water in the main pipe go. My concern is the waste of 4 min's of running water waiting for t to get hot.

    Thanks

  6. #6
    In the Trades SacCity's Avatar
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    I agree with the two Gal point of use hot water heater. I've seen several of these locoated in the cabnet under the kitchen sink and think that they are a great solution.
    Hot water instantly when you need it and then supplied by the hot water line so that there is never a point where you run out of hot water.

    I don't like the idea of using the cold water tap for two reasons, one I drink water from the tap and the cold water would no longer be cold but at some tempid temperature. Second there have been several threads here about posible issues with hot water being contaminated by crap in the water heater. So a recirc pump would distribute the crap through out the sistem.

    Michael

  7. #7
    Plumber jimbo's Avatar
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    The small tank is installed so the hot line from the wall goes to the cold inlet on the tank. You get to use the gallon plus in the tank, already hot, and by the time that is used up, the incoming heated water is now filling the tank. On a large water use, like filling a sink, there may be some variation in temp, because as soon as you open the tap, the cooled off water in the hot pipe starts diluting the heated water in the tank. 65' of 3/4" pipe is about a 1 gallons. All in all, it will be much better than what you have. If you have a dishwasher, I recommend getting one with preheat on the wash, because dishwashers perform poorly in less than very hot water.

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    DIYer, not in the trades LLigetfa's Avatar
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    Does it ever freeze in Hollywood? Maybe you could bury a dedicated return line around the perimeter of the house back to the garage and deploy a recirc pump. Any chance there is a duct or chase in/under the slab?

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Recirculation systems can be used either with using the cold water line as the return, or with a dedicated return line. It may not be all that hard to say run a return line through the attic back to the water heater. And, if you didn't need to worry about freezing, the hot attic most of the year may minimize the radiated energy loss....in fact, it might make the water hotter in the tank! When I lived in Kuwait, we had a storage tank on the roof, and the water coming out of that was so hot, it could scald you most of the year. We used the WH tank (turned off) for our cold during 9-10 months of the year, and used the 'cold' for hot. It got messy in winter when the roof tank's water was only warm, we'd usually turn the WH back on then have to remember which way to turn the valve for hot!

    I find that with mine, (it's in the master bath), that if I flush the toilet first (a common occurance), when using the sink, after the toilet has filled, the water is cold again at the cold tap. The advantage of the RedyTemp system is you have a user adjustable aquastat, you can set the temp when it shuts off. Most come preset, and you have no choice or adjustment capability. I have mine set so the water is warm, and hot is close down the pipe, but not full hot. This works fine for washing my hands, and if I do need full hot, it isn't far away in time or position. Since it is furthest from the WH, everything else has hot available, and the cold line is not really impacted since it doesn't need to pump that much back.
    Last edited by jadnashua; 04-17-2011 at 11:53 AM.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    General Engineering Contractor ballvalve's Avatar
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    This is a good product, but you can buy a 30 gallon for about the same.....

    http://www.tanklesswaterheatersdirec...eaters-100.asp

    And install a 115v 1500W element for 10 bucks.

    Or put this under the sink and just cut off the hot water feed line altogether:

    http://www.google.com/products/catal...d=0CEkQ8wIwAw#
    Last edited by ballvalve; 04-17-2011 at 12:00 PM.

  11. #11
    DIYer, not in the trades LLigetfa's Avatar
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    Is tepid water from the cold tap that big of a deal? I don't know anyone personally that drinks cold water straight from the tap. If it takes 4 minutes for the hot water line to go from tepid to hot, it would also take 4 minutes for the cold water line to go from tepid to cold.

    My RO filtered drinking water is stored in the fridge. The only reason I use cold water from the tap is to rinse something down the drain or to make the hot water less hot. Water for cooking comes from the RO spigot.

    I'm considering installing a Grundfos Comfort System recirc for the upstairs bath. Based on where it Tees off, it would purge half of the line to the kitchen sink.

  12. #12
    DIY Junior Member foamy's Avatar
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    Hi Ballvalve!
    And thanks to eveyone else who replied. This sounds great. How large a tank would you recommend for a 65' run? Also, there is still 65' of cold water that must be pushed out of the pipe so my understanding is that it goes into the small tank under the sink and starts to heat. Does this dilute the hot water that is in the tank under the sink?

    thanks

  13. #13
    Retired Defense Industry Engineer jadnashua's Avatar
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    Certainly, as the supply water fills the tank, replacing the hot, it will start to cool it off until the hot arrives. So, making the undersink tank big enough to dilute that cold water will keep it fairly constant.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Senior Member wjcandee's Avatar
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    I know this is an older thread but we use them as a resource, so...

    We just put in the Grundfos comfort system, based on some comments I had seen from Jim in another thread. I had re-insulated the pipes everywhere I could access them, but there is still about a 60-foot run through an inaccessible area where the water cools when not in use. It then runs into a crawl where everything is now well-insulated. It goes into the downstairs bathroom and then up a chase to two second-floor bathrooms and finally to a dressing area with separate sink. That's where we put the valve. In the other direction from the water heater is the kitchen, a wet bar, dishwasher, the laundry room and an upstairs bathroom at the end of the run. That's where we put the other valve. We had basically become used to having to run the hot for an extraordinary period of time just to get anything but cold, so we just lived with the cold water coming from the hot unless we really needed the hot, say for a shower, and then you just let it run while doing something else for a few minutes until you got the first hints of warm water. Major inconvenience and water waste. No practical way to run a dedicated return line without an extraordinary expense. However, because the runs are so long, and the systems that return through the cold line only recirculate a trickle of water, any demand-based system would be worthless. So a system that is running a dribble most of the day seemed like the best option, and that's what Grundfos's system offered with the heater-mounted pump and valves at the end of each run.

    I have to say that the system works very well.

    Even in the present hot summer, we have absolutely no issue with the cold side being hot. Because there is a lot of pipe between the sinks on which the valves are installed and the other fixtures, the cold side only gets a little warm in the vicinity of the sink on which the valve is installed, and it's gone in a moment even at that sink. As these are both lesser-used bathroom lavatory sinks whose use in any event always involves hot or warm water, one wouldn't even notice that some warm is coming momentarily from the cold side at those sinks. The cold side is cold everywhere else. But the quality of life improvement is enormous. Now, on the side with the very long run, you can step into a shower or run a bath, and just open the hot side, whereupon you get warm water in less than three seconds; you can step right in. The water that previously would go down the drain during the interminable wait before you could even step into the shower, is replaced with immediate use of that water. It takes a while for the water to get really hot on the end with the long run, but that's okay; one just starts to temper with cold as one feels it warming up. At all sinks, it's a transformation: we can wash hands in warm water, shave in warm/hot water, etc.,without having to waste time and water waiting for some warmth.

    On the side with the shorter run, where you still had to spill a lot of cold from the hot before, say, running the dishwasher, now all you do is rinse dishes with a little from the hot side or wash hands after loading the dishwasher, and you get a quick move from the instant warm to the truly hot so you can start the dishwasher. And when you fill a glass of cold water at the kitchen sink, it's truly cold because the crossover valve is a long way from there and the water has cooled by the time it returns past the kitchen sink.

    This system has really improved our quality of life and allowed us not to have to waste water or incur a substantial capital expense just to have the comfort of warm water in less than 3 seconds after opening the tap. I understand our oil bill may rise a smidge, but I will keep an eye on it to see if it justifies some additional capital expenditures. As I grow to understand how the Grundfos system works in practice, I'm confident that any increase will not be material. Accordingly, I'm only sorry that it us so long to find out about it from this forum. Thanks, Jim!
    Last edited by wjcandee; 07-20-2012 at 01:43 AM.

  15. #15
    DIY scratch-pad engineer leejosepho's Avatar
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    I use this Taco recirculation pump to bring hot water through a long run laying in the attic (installed after the line in the slab had failed):

    Name:  taco recirc.jpg
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    In my application, it gets powered and self-starts every time the bathroom light is turned on, and it does not put any noticeable amount of even tepid water into the cold line being used as a return. When the attic is cold, it runs for about 10 seconds ... and then for only one or two seconds when the attic is hot. If you do not want it to start every time someone enters the bathroom and turns on the light (like I have it wired), it has the option of being powered all the time (self-starting only once) and then being manually started via use of its trigger wire (if you supply the SPST momentary switch or a proximity sensor that might need its own power).

    On my favorite auction site, a search for "taco pump" can lead to finding one for about $60.00.
    Last edited by leejosepho; 07-20-2012 at 08:17 AM.
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