Its now or never...decisions (Two questions)

[Mudball]

We would like to consider hot water recirculation/pump. I dont think we will be installing anything after construction. What we have is new construction and will be having a concrete slab poured. The supply (PEX) lines will be ran under the slab through a chase pipe. The reason for the chase pipe is overkill for most but simply for any unforeseen reason the pipe needs to be removed then it can be and another piece can be slid back in place. The cost to install the chase pipe to me and my plumber is very minimal. (1st) I was thinking of asking my plumber to install TWO chase pipes because if we was to have hot water recirculating pump installed then the cold really needs to be separated from the hot supply pipe...right ? Well even if this is not true or necessary then my main concern is to (2nd) ask if it is cost effective to have the recirculating system installed as we understand the cheapest way to get it is through new construction installation and not retrofitting later.
Right now the measurements (measurements mentioned are straight shot and do not include bend and/or the total length of the actual route) from the hot water heater to the furthest fixture in master bath is around 12'. Furthest in guest bath is around 18'. and kitchen sink (our most used, hand washing etc...) is 25'. We have two boys that are 13 and 10 years old. We project the house to be finished in around 1 to 2 years.
We want the hot water recirculating but do you think its worth it ? Its now or never as far as Im thinking. Help with thoughts and/or suggestions.

[Peter Griffin]

Code wise, at this point it is not necessary given the distances to fixtures. However, recirc gives you the option of increasing your water heater temperature to 160 and installing ASSE 1017 tempering valves at the fixture locations. This will all but eliminate the possibility of legionnaires disease. This is something that plumbing boards have been wrestling with for years now. It is the right thing to do, but it get's a lot of opposition from building contractors due to the increased cost.

[hj]

quote; (1st) I was thinking of asking my plumber to install TWO chase pipes because if we was to have hot water recirculating pump installed then the cold really needs to be separated from the hot supply pipe...right ?

WRONG! The cold and hot pipes should ALWAYS be separated. And a circulation system will NEGATE the effect of a mixing valve, NOT make it better. DO NOTuse a mixing valve and circulation system if you are going to operate the heater at more than 135-140 degrees.

[Mudball]

Thanks for all the help and suggestions. HJ I dont see how I was wrong in separating the hot and cold as you suggested. Maybe I said it wrong or something. The reason again why I was wanting two chase pipes prior to pouring the concrete slab was to route one cold supply through one of the chase pipes and then run two hot lines through another separate chse pipe. Of course one of the two hot lines that are chased together would actually be the hot return. Am I looking at this right ?

[jimbo]

I believe what hj means is that the hot and cold NOW should be separated, or at least well insulated. Same for the recirc. line.

Recirc with a dedicated return is preferable in my opinion. There are side effects of retrofit recirc...warm water in the cold taps, and the extra hassle of finding somplace to put the pump, and someplace to plug it in.

[shacko]

thanks for all the help and suggestions. Hj i dont see how i was wrong in separating the hot and cold as you suggested. Maybe i said it wrong or something. The reason again why i was wanting two chase pipes prior to pouring the concrete slab was to route one cold supply through one of the chase pipes and then run two hot lines through another separate chse pipe. Of course one of the two hot lines that are chased together would actually be the hot return. Am i looking at this right ?

yes you are!

[Peter Griffin]

quote; (1st) I was thinking of asking my plumber to install TWO chase pipes because if we was to have hot water recirculating pump installed then the cold really needs to be separated from the hot supply pipe...right ?

WRONG! The cold and hot pipes should ALWAYS be separated. And a circulation system will NEGATE the effect of a mixing valve, NOT make it better. DO NOTuse a mixing valve and circulation system if you are going to operate the heater at more than 135-140 degrees.

www.watts.com video danger scalding lurks. 160 degrees at heater, ASSE 1017 tempering valves at all fixtures. Re-circ to entire system (keeps the lines at 160) mixing down occurs at fixtures. Yes it does seem like overkill but I think you will see it as code within 10 years.

[hj]

Tempering valves at each fixture is a VERY expensive option, and a single one at the water heater will NOT work with a circulation system.

[Peter Griffin]

Yes it is which is why nobody has adopted it yet. And yes a tempering valve at the heater is not going to work with recirc and for that matter does little to prevent legionella bacteria either.

[Mudball]

Thanks for all the help. Ive looked into your suggestions enough to say that I agree with the expense and dont believe it would be worth it. Is this legionnaires disease something that came up in conversation because of something Im specifically doing ?
If I understand correctly that increasing the temperature might eliminate it but what about the cold water ? Is there something Im having done wrong ?

[Peter Griffin]

No, not at all, I got sidetracked when you brought up re-circ lines. What I'm talking about has been kicking around code review boards for a few years now with mixed opinions and a lot of opposition from building contractors.

[Mudball]

Wheeww Im glad to hear that. Im going to do some more reading on this. Please post any links to this disease if you have something specific because I cant seem to find anything in simple terms for it when it comes to the relationship of the disease and plumbing but maybe I havent found the right site.
P.S. Maybe we will install a under-sink water heater in the kitchen since its the most widely used in the house and the furthest from the main water heater.
Thanks

[jimbo]

Thanks for all the help. Ive looked into your suggestions enough to say that I agree with the expense and dont believe it would be worth it. Is this legionnaires disease something that came up in conversation because of something Im specifically doing ?
If I understand correctly that increasing the temperature might eliminate it but what about the cold water ? Is there something Im having done wrong ?

The water tank represents an area where water can possibly stagnate. Cold water is too cold for the bacteria to thrive, and really hot kills them. In between, the bacteria can survive and at a low enough temp can thrive. I can't quote the research which would indicate a widespread issue, but it just keeps coming up!

[Mudball]

Thanks jimbo now I understand.