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Old 12-10-2016, 04:11 PM   #1
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Pipe Size Change


My kitchen sink is the furthest sink from the hot water heater. If the hot water hasn't been used in a while it can take a long time for the water to get hot. I wanted to run a smaller pipe to this sink. I was hoping to use a 1/2" PEX pipe. Right now this is a 3/4" copper pipe. The sink and a dishwasher will be the only items on this pipe. The PEX pipe will be about 30' long. Would the 1/2" PEX pipe be large enough for a sink and dishwasher?
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Old 12-10-2016, 04:19 PM   #2
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Re: Pipe Size Change


Need to be running a 3/4" line as a main run then tapping off with 1/2" to the shutoffs, then 3/8 to the sink and the dish washer.
A 1/2" main line would have 1/2 the flow of a 3/4" line.
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Old 12-10-2016, 04:34 PM   #3
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Re: Pipe Size Change


Yes, if sink and dishwasher are only things on that line you can reduce it to 1/2".

If you can run a new line that easily, you could put in a re circulation line for instant hot water at the sink, if you are willing to pay for the cost of running the pump.

Last edited by hkstroud; 12-10-2016 at 04:38 PM.
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Old 12-10-2016, 05:15 PM   #4
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Re: Pipe Size Change


My current pipes are exactly as joecaption states. I have a 3/4" pipe that changes to a 1/2" pipe right before it goes though the floor under the sink.

I did think about a re circulation pump hkstroud. I have an unfinished basement so it is very easy for me to run new plumbing lines. I guess that would be the best option to always have hot water available.

Thank you joecaption and hkstroud for the replies.
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Old 12-10-2016, 05:37 PM   #5
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Re: Pipe Size Change


Quote:
always have hot water available
Bet the wife would go for that option.

If you do it just right, you may be able to make a re circulation line work with out a pump.

Last edited by hkstroud; 12-10-2016 at 05:43 PM.
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Old 12-10-2016, 06:16 PM   #6
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Re: Pipe Size Change


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Originally Posted by hkstroud View Post
If you do it just right, you may be able to make a re circulation line work with out a pump.
After looking at the prices of pumps I might try this option first. I could always add a pump if I need to.
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Old 12-10-2016, 06:20 PM   #7
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Re: Pipe Size Change


Besides the cost of pump and electricity. You have to add the cost of keeping that line hot 24x7.

So make sure you at least insulate the pipe good.
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Old 12-10-2016, 06:45 PM   #8
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Re: Pipe Size Change


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Besides the cost of pump and electricity. You have to add the cost of keeping that line hot 24x7.

So make sure you at least insulate the pipe good.

That's right. Your HW tank will be getting a constant return flow of cool water.


I have the PEX set up you asked about. 3/4" main lines and manifold. Off the manifold are 1/2" pex lines direct to the fixtures. My kit. sink line branches off under sink and feeds the DW also. Distance is probably 25' of 1/2" pex. It takes about 5 seconds for the hot water to reach the tap.

It also helps to keep your hot water manifold as close to the tank as possible to reduce the length of the 3/4 lines. I place it directly above the HW tank.
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Old 12-10-2016, 09:26 PM   #9
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Re: Pipe Size Change


To save electricity, most people here put their recirc Pumps on timers. (they only need the pump during quiet times) The flow actually doesn't need to be very high at all, but I'm not a plumber.

Insulating the pipes is also a great suggestion.

Cheers!
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