Rossn
Member
Hello,
I am looking for some recommendations on a challenging hot water recirculation design issue. Apologies in advance for the wordy post, as it's a complicated situation:
I'm remodeling a good portion of my home and am adding a bedroom/bath above the garage, which requires about 100' on the hot water line. Additionally, I have a bath about mid-way (50') , which historically has taken quite a long time to get hot water to the lavatory. On the attached diagram, these are on the right/east end. The room above the garage may sometime have a roommate and get used regularly, and at other times it may be empty with virtually no use. The other East bath is intended for office/guest room use, and is planned for intermittent use, but if we have another child, could be used more frequently.
The consistently used area of the house would be the kitchen and 2.5 baths on the west end of the home. Nothing here has a major hot water issue, though the far west lavatory and shower do take around 30 seconds to get hot water.
The boiler and side arm are between the two areas, and shown on the diagram.
I'm interested in installing a dedicated hot water recirculation return line (house is gutted currently), as I'm not keen on the nature of pushing hot water from the cold to hot side because a) the nature of warming the cold water side b) we drink water from the tap c) the fact that in Colorado, ground water can be quite cold in the winter, and this could draw colder water into the side arm, thus being more likely to trip on the boiler
One of my primary concerns is wasting energy from hot water sitting in the line, going cold, which is why I'm gravitating towards an on-demand/push button type system like D'MAND (http://www.gothotwater.com/), and installing the pump on the 'far end' so as to not also have hot water sitting in the recirculation line. Along with this goes the fact that I don't want to kick on the boiler more than absolutely necessary.
I haven't been able to come up with a solution that meets my energy desires, provides hot water, and also sources both the frequently used areas and the intermittently used areas, while using a single pump.
Summary of design goals:
- Must have DHW recirculation on two east end bathrooms, which may see intermittent or regular use
- Prefer DWH recirculation on frequently used W end areas, though not mandatory (1 shower and lav are slow to get hot water ~30 seconds). Single pump would be nice, but not if it dramatically increases energy waste.
- Boiler is approximately between the two areas
- Want to be very mindful of energy use from both hot water sitting in the hot water line and the boiler kicking on more frequently
- Want to be mindful of maintenance and pipe longevity
Questions:
1) What is the design recommendation for pump placement and recirculation line(s)
2) I have read that higher velocities can cause pin-hole leaks. Is this real? I was intending to use the D'MAND pump on the highest setting, to reduce the time to getting water to the far end. If real, would I be better off using PEX on the hot water side (was intending to use copper throughout)
3) How practical is the issue of kicking on the boiler much more frequently?
4) Are there other solutions I should be looking to?
Thanks in advance for all the help!
Some tech info:
Approx. ONE WAY distances and volumes for DHW line of varying options based on 3/4" copper:
Downstairs:
I am looking for some recommendations on a challenging hot water recirculation design issue. Apologies in advance for the wordy post, as it's a complicated situation:
I'm remodeling a good portion of my home and am adding a bedroom/bath above the garage, which requires about 100' on the hot water line. Additionally, I have a bath about mid-way (50') , which historically has taken quite a long time to get hot water to the lavatory. On the attached diagram, these are on the right/east end. The room above the garage may sometime have a roommate and get used regularly, and at other times it may be empty with virtually no use. The other East bath is intended for office/guest room use, and is planned for intermittent use, but if we have another child, could be used more frequently.
The consistently used area of the house would be the kitchen and 2.5 baths on the west end of the home. Nothing here has a major hot water issue, though the far west lavatory and shower do take around 30 seconds to get hot water.
The boiler and side arm are between the two areas, and shown on the diagram.
I'm interested in installing a dedicated hot water recirculation return line (house is gutted currently), as I'm not keen on the nature of pushing hot water from the cold to hot side because a) the nature of warming the cold water side b) we drink water from the tap c) the fact that in Colorado, ground water can be quite cold in the winter, and this could draw colder water into the side arm, thus being more likely to trip on the boiler
One of my primary concerns is wasting energy from hot water sitting in the line, going cold, which is why I'm gravitating towards an on-demand/push button type system like D'MAND (http://www.gothotwater.com/), and installing the pump on the 'far end' so as to not also have hot water sitting in the recirculation line. Along with this goes the fact that I don't want to kick on the boiler more than absolutely necessary.
I haven't been able to come up with a solution that meets my energy desires, provides hot water, and also sources both the frequently used areas and the intermittently used areas, while using a single pump.
Summary of design goals:
- Must have DHW recirculation on two east end bathrooms, which may see intermittent or regular use
- Prefer DWH recirculation on frequently used W end areas, though not mandatory (1 shower and lav are slow to get hot water ~30 seconds). Single pump would be nice, but not if it dramatically increases energy waste.
- Boiler is approximately between the two areas
- Want to be very mindful of energy use from both hot water sitting in the hot water line and the boiler kicking on more frequently
- Want to be mindful of maintenance and pipe longevity
Questions:
1) What is the design recommendation for pump placement and recirculation line(s)
2) I have read that higher velocities can cause pin-hole leaks. Is this real? I was intending to use the D'MAND pump on the highest setting, to reduce the time to getting water to the far end. If real, would I be better off using PEX on the hot water side (was intending to use copper throughout)
3) How practical is the issue of kicking on the boiler much more frequently?
4) Are there other solutions I should be looking to?
Thanks in advance for all the help!
Some tech info:
Approx. ONE WAY distances and volumes for DHW line of varying options based on 3/4" copper:
- W End Loop, no Kitchen = 40’ (0.9 gal 1-way)
- W End Loop, w/ Kitchen = 48’ (1.1 gal 1-way)
- E Bath Loop (no Garage) = 54’ (1.2 gal 1-way)
- Garage/E Bath Loop w/ pump under vanity = 102’ (2.3 gal 1-way)
- Garage/E Bath Loop w/ pump under kitchen = 108’ (2.4 gal 1-way)
- Garage/E Bath Loop w/ pump under stairs = 112’ (2.5 gal 1-way)
- Main House Loop = 106’ (2.4 gal 1-way)
- Single Combined loop = 143’/173’ (3.2/3.9 gal 1-way; to kitchen vs to bath)
Downstairs: