Are there disadvantages to wider supply pipes?

[gadolphus32]

I'm planning to replace all of the cold and hot water supply lines in my basement. Currently, the supply coming into the house is 3/4 inch copper. Right after the main shutoff, it goes down to 1/2 inch, and all the other pipes in the house are 1/2 inch.

My main reason for replacing the pipes is to reduce lead in the water (on that, see below) but the water flow in my house is also a little weaker than I would like. In the hope of improving it, I plan to replace the 1/2 inch pipes with 3/4 inch as much as possible.

I'm not going to replace the pipes in the finished parts of the house. Those will still be 1/2 inch. I'm just replacing the exposed pipes in the basement. I'll reduce everything down to 1/2 inch where it goes upstairs.

I'm wondering if there is any reason *not* to want to have 3/4 inch rather than 1/2 inch lines. Apart from the slightly higher cost of 3/4 inch pipes and fittings, I can't think of any obvious disadvantage, but I'm also not a professional plumber.

In case it matters, the pipes are currently all copper. I'll replace them with Pex. The replacement is motivated by a desire to reduce lead levels in my water, which tested higher than acceptable even though we do not have lead pipes. I suspect the 100-year-old solder is the culprit, and I hope that by replacing as much piping as I can with Pex, I'll be able to reduce the lead levels significantly.

 

[Cacher_Chick]

Normally the main trunk lines are 3/4", and branches for fixtures are 1/2".
The problem with going oversized is on the hot water, one has to run that much more water down the drain waiting for the heated water to arrive at the fixture.

 

[Sponsor]

 

[gadolphus32]

The problem with going oversized is on the hot water, one has to run that much more water down the drain waiting for the heated water to arrive at the fixture.

That is an excellent point. I'm glad I asked

Any reason not to do 3/4 inch for the cold water and 1/2 inch for hot? Would 3/4 inch cold be likely to improve water flow in the house (even though there'd be a reduction to 1/2 inch before the water reached the faucets)?

Part of my thinking here, by the way, is that Pex couplings would create smaller water flow diameters because the Pex fittings go inside the pipe, whereas with brass fittings and copper pipe you don't add any blockage to the inside of the pipe with the fitting. So part of me wonders if I need 3/4 inch Pex in order to get water flow equivalent to 1/2 inch copper.

 

[hj]

PEX is significantly smaller than copper so using 3/4" PEX will probably be the same as your current 1/2" piping, and I doubt that you will make ANY difference in the lead content, since ANY lead that was going to leach out of the solder has done so LONG ago, (and even then it would have only done it for a very short time until the solder was coated with a patina layer isolating it from the water).

 

[Cacher_Chick]

Yes, when working in PEX, the main trunk lines should be one size larger than that of the equivalent copper. It is also good practice to home run the fixtures that use most of the water, such as the tub, shower, laundry, hose spigots, etc.

 

[PorcelainVacation]

It seems like you would want to break the line at the entry to the house and check the incoming water for lead. As others have said, it may not be your pipes at fault. Your city water quality department should be able to help you troubleshoot.

 

[Themp]

My house was built in 1984 with all copper and 50-50 tin/lead solder. When the ban on the lead type solder took affect we always ran the kitchen sink cold water in the morning for a bit to flush the lines. We also decided to use a Brita filter for coffee and other things that needed water for cooking. Then about 10-15 years ago our city decided that any house built before 1986 that had copper piping had to be tested. They sent us a bottle that we had to fill from the kitchen cold line faucet in the morning after sitting all night. It came back negative for high levels of lead. We still do the flush and Brita thing, but it seems the comment on a patina happening, happened to us.

 

[Terry]

I quit using 50/50 lead solder before it became code. I had young kids and didn't want to bring back lead on my clothes.
I found that I was getting fewer leaks from the framers banging on walls while I was soldering. I reported that to the other plumbers, fewer leaks. Soon most of the shop had switched over to the no-lead solder.
It's impossible to break a no-lead joint, but I've seen 50/50 joints that have been broken.