Replacing old galvanized steel plumbing with PEX

[John5337]

I had two questions... One, should I run the PEX the same way the old galvanized steel or maybe use a manifold and run it differently? And my second question is, my bathtub currently has 1/2 inch galvanized steel, should I stick with 1/2 PEX or do you think I should run 3/4, or would I lose pressure if I were to use 3/4 PEX instead or 1/2? Thanks!

 

[Terry]

Most tubs are run with 1/2" PEX except for the tub spout.

 

[Sponsor]

 

[John5337]

That's what I was thinking... But I wanted an option of an expert, thanks!

 

[John5337]

Also, would you recommend using a manifold or just run the plumbing the same way the galvanized steel is?

 

[Terry]

The choice of a manifold or replacing the layout as it was done is easier to determine onsite.
I have done it both ways. It kind of depends on your access. The manifold system does unload the hot line quicker. You're emptying a smaller line to get hot to the shower. And you're still balanced at the water heater pulling from the 3/4" there.

 

[Tuttles Revenge]

Also depends on the type of manifold you're referring to. I stopped installing the big distribution manifolds a Long time ago because I prefer installing hot water recirculating systems for fastest hot water delivery. But there are point of use manifolds that save time and fittings which are perfectly fine for recirculating through and allow you to run a 3/4 line to a distribution manifold and short runs up to each fixture.

New PEX is going to deliver vastly larger volumes of water compared to an old rusty galvanized line even with a moderate reduction in fitting volume. Once you cut out a single 12" piece of galvy and try to look through it end to end you will see why.

 

[Dave Millman]

So I had a great local plumber replace galvanized with PEX five years ago. All the pipes they cut out were filled with corrosion like in Tuttle's photo. We chose to route the PEX like the old galvanized pipes.

Soon thereafter, the gas water heater failed. It was a decent Bradford White, still under warranty, installed by the same firm. The plumber contacted Bradford White, who authorized a new control unit, at no cost to me.

Within a week the water heater failed again. The plumber and I got on the phone with the pro support tech at Bradford White. After 20 minutes the tech said, "As long as the unit is grounded properly to the pipes this shouldn't be happening."

Bingo. The copper ground r0d was at the electrical service panel on the far side of the house, and the old galvanized pipes had been strapped to ground nearby. When they replaced the galvanized pipes, the gas water heater in the garage was no longer grounded through the plastic PEX. I installed a new ground strap and it has worked perfectly ever since.

 

[Terry]

I installed a new ground strap and it has worked perfectly ever since.

That's really good information.

When we do a repipe of galvanized or copper, the first check is to see how the electrical panel is grounded. If they are using the water lines for a ground, the electrician needs to be called out to install grounds for the panel first. Plumbers have died while doing repipes when the grounding wasn't corrected first.

Grounding the water heater is new to me. Thanks for the information.