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Old 12-17-2012, 11:58 AM   #1
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Supply Line Sizing with PEX


We are redoing all the supply lines in 160 year old home that had galvanized piping. The house has a kitchen/laundry in the basement, 1/2 bath and kitchen on the first floor, 3 full baths on the 2nd floor, and 1 full bath on the 3rd floor. Was thinking of running 4 separate 3/4 inch cold water trunks and hot water loops as follows:
1) basement and 1st floor fixtures
2) 1 - 2nd floor bath (on opposite side of house from the other two)
3) 2 - 2nd floor baths
4) 3rd floor bath

We are on a well with a pressure tank set with 40/60 cut in/out. Max distance is approx. 120ft between pressure tank and 3rd floor fixtures. Approx. 35 ft of that would be vertical.

Any other suggestions or possible issues with my layout would be appreciated.

Supply Line Sizing with PEX-supply-plumbing-4-loop-11-08.jpg

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Old 12-17-2012, 12:59 PM   #2
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Supply Line Sizing with PEX


Are you using 4 recirc pumps? Why so many loops? Are the fixtures so remote that it requires so many pumps? Seems like you could cut back on the pumps and pipe by using circuit setters. You have a lot of hw lines that are wasting energy.

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Old 12-17-2012, 01:33 PM   #3
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Each loop does have its own pump so yes there are 4 in the drawing. Thought about going to 3 loops (combine the basement/1st/2nd floors on the one side of the house). The other 2nd floor bath is fairly remote and the 3rd floor would have minimal use so thought it would make sense to keep it separate. Not sure what a circuit setter is, first I've heard of it. Will google it some but can you elaborate on how it would be used here?

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Old 12-17-2012, 01:57 PM   #4
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Supply Line Sizing with PEX


Do a Water Supply Fixture Unit calculation:

http://www.engineeringtoolbox.com/Wa...ts-d_1073.html

http://www.engineeringtoolbox.com/wf...es-d_1075.html

For example, to feed two bathrooms (7.5 WSFU each = 15WSFU), at 46-60PSI, 120 feet away, you need 1" pipe. I believe the vertical run of a pipe for multistory dwellings also comes into play, but my house is only a single story so I didn't research that part.

In most cases, 1/2" is the minimum. You can run a big pipe to a bathroom area and tee off from there to a bunch of 1/2" lines going to each individual fixture.

Note, using the calculation, hot main trunk lines can sometimes be smaller than the cold, since toilets and hose bibs don't use hot water.

Don't forget pipe insulation too, otherwise your hot water bill will be scary. Where possible, I'd also use fiberglass or cellulose in the stud / joist bays that the pipe runs through.
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Old 12-17-2012, 01:58 PM   #5
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A circuit setter is a glorified ball valve. It has an indicator dial so you know how open/closed the valve is. Also has test ports so you can read the GPM through the valve. We use them on recirc lines that have loops to other areas of a building. They allow you to balance the flow equally to the recirc branches.
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Old 12-17-2012, 02:32 PM   #6
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I never saw loops in potable water supplies, new on me and I'm 66, but I dont do this for a living. Seems like maybe 2 on demand water heaters under the sinks could eliminate a lot of this.
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Old 12-17-2012, 03:05 PM   #7
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Seems like maybe 2 on demand water heaters under the sinks could eliminate a lot of this.
That's true, and depending on heat losses in the pipes, may even be more energy efficient. But on-demand units will probably require running new dedicated electrical circuits, which is probably about as expensive as recirc lines.
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Old 12-17-2012, 03:22 PM   #8
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Originally Posted by tylernt View Post
That's true, and depending on heat losses in the pipes, may even be more energy efficient. But on-demand units will probably require running new dedicated electrical circuits, which is probably about as expensive as recirc lines.
Aren't the undersink hotwater heaters typically just for the sink demand? Still need to get hot water to the tub/showers right?
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Old 12-17-2012, 03:30 PM   #9
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I never saw loops in potable water supplies, new on me and I'm 66, but I dont do this for a living. Seems like maybe 2 on demand water heaters under the sinks could eliminate a lot of this.
The recirc loops are just on the hot water. Used mainly for remote or long runs so that the water that has cooled in the hot water lines goes back to the hot water tank instead of down the drain. I.e. I don't need to stand in the tub running water for 1 minute or more waiting for the water to get hot. They are controlled by either timers or manual control that can be pushed when you get up, you enter the bathroom or whatever.
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Old 12-17-2012, 03:32 PM   #10
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Originally Posted by TheEplumber View Post
A circuit setter is a glorified ball valve. It has an indicator dial so you know how open/closed the valve is. Also has test ports so you can read the GPM through the valve. We use them on recirc lines that have loops to other areas of a building. They allow you to balance the flow equally to the recirc branches.
Most of what I've found about them read like more for boiler water type scenarios. I see potable mentioned but not sure how to set them into what I have.
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Old 12-17-2012, 03:36 PM   #11
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Aren't the undersink hotwater heaters typically just for the sink demand? Still need to get hot water to the tub/showers right?
Since it doesn't take as long to get hot water a long distance through a fully open tub valve, just point-heating the sink and feeding the tub with the distant main heater would work.

What I've also seen done is putting in a medium size point heater, and feeding it with the distant hot water. The idea is before the point heater is exhausted, hot water has finally arrived from the distant heater, so you get a steady supply of hot.
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Old 12-17-2012, 03:41 PM   #12
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I had to stand there and wait, but I didnt wait in the tub

No I own a Ranch, and the HWH is very close to the bathrooms below.

Kitchen is a pain though, on the far end. How does the recirculator work on a timer? or thermostatic control?

This sounds like an energy hog
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Old 12-17-2012, 03:55 PM   #13
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Kitchen is a pain though, on the far end. How does the recirculator work on a timer? or thermostatic control?
We have the same thing in reverse, kitchen is close, 2 bathrooms at the opposite end of the house. Either waste 1 minute and a gallon of water to get hot water, or just wash in cold. Ugh.
Quote:
This sounds like an energy hog
Done wrong, it can be.

There are many options. The one we used has both a timer and a thermostat (Laing is the brand, but Grundfos also appears to make a good pump). I set it to be active from 7am to 10pm. Between those times, the thermostat controls the pump. It will come on first thing in the morning and shut off when it senses hot water in the return line. Then it waits until it cools off and then runs again until it senses hot water.

For this type of application, it's critical that you insulate your hot water pipes. Failure to insulate means the pump runs a lot and your water heater has to keep heating and reheating that water, only to immediately lose the heat to the spaces the pipe runs through.

Electrically, a thermostatic pump doesn't draw much because it's only 11W and it runs for maybe 1 minute every half hour or so. You just have the heat loss through the pipe insulation to deal with. Your water heater will fire a little more frequently than usual. Better pipe insulation means less firing, hence my recommendation to add wall insulation to the spaces the pipe runs through.

Alternatively, you can get a pump with no thermostat and no timer, just a button. When you enter the bathroom, you push the button. About a minute later, you have hot water. This saves more energy and while pipe insulation here still helps, it's not as critical since you're not recirculating very often.

In either case, you waste less water. This could be important if you are in a drought area or on a private well that tends to go dry (like mine).
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Old 12-17-2012, 04:24 PM   #14
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I don't know the layout of your bathrooms and kitchens but it seems like you could do all this on one loop- 1 pump. Start off the heater and end on the top floor and return back to the heater. Any fixture you missed going up can be piped coming down.
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Old 12-18-2012, 08:18 AM   #15
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I don't know the layout of your bathrooms and kitchens but it seems like you could do all this on one loop- 1 pump. Start off the heater and end on the top floor and return back to the heater. Any fixture you missed going up can be piped coming down.
That would look something like the attached. I have the cold trunk on 1", not sure it needs to be that big. Maybe hot water needs to be 1" as well? Or should 3/4" work for all? I had mentioned the 1" cold trunk to the plumbing inspector and he thought I might have pressure issues, he also thought the extra head to the 3rd floor might be better off separated to a different line than the 2nd and 1st floors, I think he said it would cause an excessive pressure drop to the to the other fixtures. This is the first time I'm dealing with the large number of fixtures or anything more than 2 floors but mainly I'm trying to avoid what I've had in other homes we've lived in where multiple fixtures affect each other temperature (i.e. scalding or freezing when someone turns another fixture in the house on) or large pressure differences when another fixture is turned on.

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