Some musings about copper pipe

[ss55]

I replumbed the entire house when I remodeled 12 years ago. Used type M copper pipe throughout.
Some simple arithmetic shows that to get hot water to the kitchen sink - or to a 1/2 bath at that end of the house we are heating 10 lbs of copper pipe each time we wash our hands or rinse a cup.
I am thinking about replacing the copper hot water pipe with Pex. The heat loss would be much less so less energy used, we would get hot water sooner and we'd use less water.
The water lines are exposed and run across the joists in the cool basement so it would be an easy job to run the pex in the same pipe hangers that the copper is in.
I have the skills and the pex tools so it would be afternoon's work and maybe $60 in parts.
I'm thinking it's worth doing but what says the brain trust here?

Think about how many gallons of room temperature water are sitting in the pipe between the faucet and the water heater, maybe several gallons in a long pipe run. That water must be displaced (flow out the faucet) before any hot water can reach the faucet. A smaller diameter pipe (bad when filling a bath tub or large sink) or a recirculating pump will help get hot water to the distant faucets faster. Insulating the pipe will slow the heat loss, but will not help much at any faucet that is used infrequently.

 

[ss55]

How about having a switch on the recirculating pump, and turning it on only when needed?

2X on the switch! Some units have a push button and timer that run the pump a set amount of time, just enough to get hot water to the faucet. Thirty seconds later hot water is at the faucet without wasting any water.

 

[da.bees]

x3 on the switch AND a reason for using one vs conventional recirculating system. From my short stint with multi-family properties I learned that circulating water soon wears through heavy wall copper. As an aside , the buildings are rode so hard and hung up wet they are also wearing thin pretty quick.

 

[Tony in SD]

How about having a switch on the recirculating pump, and turning it on only when needed?

I have a programable switch on my recirculating pump. It only comes on during the day when hot water is expected to be used.

 

[JMOR]

Maybe I'm just lucky, but my recirculating hot water loop has been running for 25 years (3rd pump) and so far no worn thru piping and hot water instantly. Keep me lucky, please.

 

[da.bees]

Maybe I'm just lucky, but my recirculating hot water loop has been running for 25 years (3rd pump) and so far no worn thru piping and hot water instantly. Keep me lucky, please.

Not to spoil you luck but a couple of leaks I dealt with were only discovered incidental to complaints about air conditioning. All the king's horses and men worked on ac but tenants continued to complain. When I investigated I found apartments being heated by hot water leaking beneath concrete slab foundation.

 

[JMOR]

Not to spoil you luck but a couple of leaks I dealt with were only discovered incidental to complaints about air conditioning. All the king's horses and men worked on ac but tenants continued to complain. When I investigated I found apartments being heated by hot water leaking beneath concrete slab foundation.

I expect improper joints.

 

[Ultradog MN]

I replumbed the entire house when I remodeled 12 years ago. Used type M copper pipe throughout.
Some simple arithmetic shows that to get hot water to the kitchen sink - or to a 1/2 bath at that end of the house we are heating 10 lbs of copper pipe each time we wash our hands or rinse a cup.
I am thinking about replacing the copper hot water pipe with Pex. The heat loss would be much less so less energy used, we would get hot water sooner and we'd use less water.
The water lines are exposed and run across the joists in the cool basement so it would be an easy job to run the pex in the same pipe hangers that the copper is in.
I have the skills and the pex tools so it would be afternoon's work and maybe $60 in parts.
I'm thinking it's worth doing but what says the brain trust here?

All good and interesting replies fellas.
Thanks.
I mentioned here before that I am finishing a 3rd bathroom that I framed in when we added on.
It is on that end of the house so the hot water will need to travel another 15 feet or so.
So I am going to go ahead and replace the hot line with pex all the way back to the water heater. But before I do I think I will try an experiment to see how many seconds and gallons it takes to get the water to max temp at the kitchen sink with the copper. Then do the same test with the new pex.
I will post back with the results soon.
I will take you guy's advice and insulate that line tho. Should have done that before..
Thanks to the brain trust here.

 

[Hemmjo]

How about a circulating pump in the hot water line at the sink farthest from the water heater?...Actually I think it could be anywhere in the line. Maybe a plumber on here could enlighten us tho'

Hot Water Recirculating Pump: What To Know Before You Buy

Tired of waiting for the shower to heat up? Save time, water and money with a hot water recirculating pump.

www.familyhandyman.com

Some people install a small constantly operating recirculating pump loop their hot water lines. Unless you have money to burn, this a bad idea. There is so much heat loss from a system like this.

I did install a recirculating pump for a elderly couple some time ago. They wanted one so I installed it, BUT, I put a timer switch on the pump. When you are going to shower, turn the switch on, it will run the pump for 5-10-15 minutes, whatever you choose. Warm the hot water line, not waste water, then turn off.

They loved it.

 

[BarnyardEngineering]

All good and interesting replies fellas.
Thanks.
I mentioned here before that I am finishing a 3rd bathroom that I framed in when we added on.
It is on that end of the house so the hot water will need to travel another 15 feet or so.
So I am going to go ahead and replace the hot line with pex all the way back to the water heater. But before I do I think I will try an experiment to see how many seconds and gallons it takes to get the water to max temp at the kitchen sink with the copper. Then do the same test with the new pex.
I will post back with the results soon.
I will take you guy's advice and insulate that line tho. Should have done that before..
Thanks to the brain trust here.

Unless you use the hot water frequently, insulating the line won't make much difference in how fast the hot water reaches the faucet. Insulation only slows the flow of heat. It does not stop it. This is why your furnace still runs in the winter even if you have tons of insulation in the house.

After sitting from breakfast until dinner, or overnight, the water in that pipe is going to be just as cold as if there were no insulation at all. You're still going to be standing there for however long, waiting for the cold water to purge from the pipe, wasting water.

The best solution would be to add that auxiliary water heater in the supply line to the kitchen and bath. That, or relocate the main water heater to where the bulk of the hot water usage is.

 

[Russ from MN]

All good and interesting replies fellas.
Thanks.
I mentioned here before that I am finishing a 3rd bathroom that I framed in when we added on.
It is on that end of the house so the hot water will need to travel another 15 feet or so.
So I am going to go ahead and replace the hot line with pex all the way back to the water heater. But before I do I think I will try an experiment to see how many seconds and gallons it takes to get the water to max temp at the kitchen sink with the copper. Then do the same test with the new pex.
I will post back with the results soon.
I will take you guy's advice and insulate that line tho. Should have done that before..
Thanks to the brain trust here.

I look forward to the results of your test!

 

[JMOR]

I look forward to the results of your test!

Just the change from copper to pex would have been interesting, but the simultaneous addition of insulation kills that.

 

[Keith True]

If it is just for a sink I would go to 3/8 pex for the hot.The real life difference is almost not noticeable.3/8 pex holds exactly 1/2 gallon of water per 100 feet.1/2 copper,(M) holds 1-1/3 per 100 feet.Those are the amounts you have to move before the hot stuff gets to you.I fed my bathroom with 3/4 pex,but only because I wanted to fill a walk in tub faster.I used a 3/8 line run alongside the big hot pex,just for the bathroom sink.Remember,your supply lines at the point of use are only 3/8,and the little disc in the faucets are only 1/8.You just don't need a lot of volume for a bathroom sink.

 

[drsportster]

Insulation of pipes ?

 

[olddavid]

While installing a recirculating pump will get you hot water much faster I don't think it is worth it. You will save a little water but your energy bills will be higher. You have to power the pump and reheat the water that is circulating around. It also makes the system more complex. In my opinion complexity and reliability are inversely proportional.

 

[JMOR]

While installing a recirculating pump will get you hot water much faster I don't think it is worth it. You will save a little water but your energy bills will be higher. You have to power the pump and reheat the water that is circulating around. It also makes the system more complex. In my opinion complexity and reliability are inversely proportional.

10,000 sq feet vs 1500 probably matters, too.

 

[Ultradog MN]

Just the change from copper to pex would have been interesting, but the simultaneous addition of insulation kills that.

JMOR,
Adding on to the length shouldn't matter because the kitchen and half bath are upstream from the 3rd bath.

 

[DRussell]

I replumbed the entire house when I remodeled 12 years ago. Used type M copper pipe throughout.
Some simple arithmetic shows that to get hot water to the kitchen sink - or to a 1/2 bath at that end of the house we are heating 10 lbs of copper pipe each time we wash our hands or rinse a cup.
I am thinking about replacing the copper hot water pipe with Pex. The heat loss would be much less so less energy used, we would get hot water sooner and we'd use less water.
The water lines are exposed and run across the joists in the cool basement so it would be an easy job to run the pex in the same pipe hangers that the copper is in.
I have the skills and the pex tools so it would be afternoon's work and maybe $60 in parts.
I'm thinking it's worth doing but what says the brain trust here?

Is your goal energy savings or faster hot water?

 

[Ultradog MN]

Is your goal energy savings or faster hot water?

Mostly faster hot water.
But faster hot water would also give an energy savings and use less water.
I'm not disagreeing with anyone here.
But here is my thinking:
Yes, I will insulate the pipe after I install the pex.
Should have done that long ago.
First, the basement is pretty cool - about 60 degrees in winter. Yes, the insulation will keep the pipe warmer longer.
But after the water in the kitchen has been unused for several hours, insulated or not the pipe will inevitably cool down to 60 degrees.
Second, I was able to compute the total weight of the copper pipe I'm warming - it's about 10 lbs. I did not find specs on the weight of pex.
However, go to Home Depot and grab a 10' stick of copper pipe in one hand and a stick of pex in the other.
I'm guessing the pex weighs 1/4 to 1/3 of what the copper weighs. So I would be warming 66-75% less weight in pipe which might? speed up getting hot water where I want it - might? use a wee bit less energy and - might? use a little less water.
Is it worth doing?
I don't know.
But I'm willing to spend a few $ to experiment even if it is wasted.
I've wasted more $ on dumber things before.
Just look at the old tractors and junk I have.

 

[Mule Meat]

Insulted or not. Copper or pex. Neither one will help you get hot water faster.

1/2" copper or 1/2" pex. Once the water is cooled to X degrees in the line. The hot water must push that cold water out before the hot water can exit the faucet. It does not matter if the wall of the line is 1/32" thick or 12". How fast the line heats up is nothing but an indicator as to how well the line can conduct heat from the hot water and transfer it to the wall of the line.

Want hot water quicker? Find a way to make the smallest amount possible of cold water that the hot must push before it exists the faucet.