Are recirculating loops/pumps dangerous for my house?

[JoeSD]

When we remodeled our house in 2016 we had the whole house replumbed and they put in a recirc loop with dedicated return line. I've recently read though that recirc loops are notorious for causing copper issues due to the high velocity and hot water. Should I just turn the pump off and stop using recirc line?

 

[Breplum]

Well, we certainly don't like to see short turn copper 90s and such. The primary issue is high velocity pumps installed by idiots who don't know what they are doing.
Make sure you have low velocity and you should be good.

 

[Sponsor]

 

[John Gayewski]

What size pipe did they use. 1/2 pipe was the norm for a long time which did cause velocity issues. As long as the recirc line is 3/4" pipe you should be good. That is, as long as you have the smallest pump made for these things.

 

[Fitter30]

Ask yourself can i hear loud water noises rushing through the pipes? Not don't worry about it. Never have seen copper pipe erosion in 40 years.

 

[Tuttles Revenge]

I have seen copper pipe wear out from too much velocity in a too small recirc line. Happened on a job the second day after start of work and the homeowner thought the carpenters caused it. We ended up replacing the 1/2" copper return with a 3/4 PEX with lower volume pump.

 

[JoeSD]

Ask yourself can i hear loud water noises rushing through the pipes? Not don't worry about it. Never have seen copper pipe erosion in 40 years.

I can't hear any water rushing its always dead silent.

What size pipe did they use. 1/2 pipe was the norm for a long time which did cause velocity issues. As long as the recirc line is 3/4" pipe you should be good. That is, as long as you have the smallest pump made for these things.

I went and looked, he used 1/2" pipe, it was done back in 2016. Disappointing he didn't use 3/4"

Well, we certainly don't like to see short turn copper 90s and such. The primary issue is high velocity pumps installed by idiots who don't know what they are doing.
Make sure you have low velocity and you should be good.

I was here a lot when they were renovating the house and replumbing everything and saw everything with the walls opened, the recirc loop is a big long run from the garage to the kitchen with lots of straight and not many turns. I found the model of the pump, it's a GrundFos UP 15-10 B5/TLC with a flow rate of 2.77 US GPM. Is that low or high velocity?

 

[Breplum]

It is a good 1/25th HP low velocity pump.

 

[Fitter30]

I can't hear any water rushing its always dead silent.

I went and looked, he used 1/2" pipe, it was done back in 2016. Disappointing he didn't use 3/4"


I was here a lot when they were renovating the house and replumbing everything and saw everything with the walls opened, the recirc loop is a big long run from the garage to the kitchen with lots of straight and not many turns. I found the model of the pump, it's a GrundFos UP 15-10 B5/TLC with a flow rate of 2.77 US GPM. Is that low or high velocity?

max flow 3.2 gpm
100' 1/2". m holds 1.2 gallons
100' 3/4" m holds 2.25 gallons

 

[John Gayewski]

Roughly a 1/2" line at 2.8gpm should be traveling at around 3ft.per sec

At 3.2 gpm it should be about 3.4 ft per sec.

You should be under the max for 1/2copper. Which (going from memory) is about 4ft per sec.

If that pump does what you say it does you should be good.

 

[John Gayewski]

 

[JoeSD]

View attachment 98799

I measured our water temp with an instant read thermometer and looks like we have ours at 130 degrees F.

 

[John Gayewski]

I measured our water temp with an instant read thermometer and looks like we have ours at 130 degrees F.

Sounds like your should be below the max.

 

[Jeff H Young]

I dont know the tricks to dialing in the system but a flow control "circuite setter" can slow it down a bit more if you want ? getting effeciency I dont know there again are a lot of factors , a whole house recirculating system thats left on and allowed to run and keep pipes hot a bit differant from one where you walk in a bathroom and the system kicks on and gets hot water to the area that might take more speed to do it quickly but pump runs shorter amounts of time.
But a well plumbed recirc system should be enjoyed and last a long time I wouldnt expect cost a bunch in energy if done right

 

[gillrich]

While recirculation loops are convenient for quickly delivering hot water throughout the house, they can indeed lead to accelerated corrosion in copper pipes due to the high velocity and temperature of the water.