Learn me: replacing a gas water heater with an electric.

Our house turns 22 this summer so we've been doing some renovation. We replaced our gas furnace with a heat pump system and we're in the process of getting solar installed. Our utility has a program where they will give you a $2000 rebate if you replace your gas water heater with a hybrid/heat pump unit. That basically covers the cost of the unit.

I have a plan for the plumbing but I'd appreciate any feedback you all could give me. I'm pretty OCD so I'm trying to keep all of the runs as short and straight as possible.

The copper comes straight out of the wall at 70" from the floor. The old WH is about 60" tall has the inlet and outlet on the top. The new WH is 65" tall. The inlet at the bottom/center/front as your facing the unit. The outlet is on the upper third/left/front. I'm planning to put a straight Shark Bite connector on the copper at the wall, run a straight section of 3/4" Pex over the WH, add a 90 connector so the lines run straight down the front and then use a 90 connector into the WH. Does this seem reasonable?

Old WH:

New WH:

That's the most ridiculous (new) water heater I've ever seen!  Some engineer should be shot. 
 

Yeah, that sound fine. Don't forget your shutoffs (use ball valves instead of the gate valves you've got). I would also install a threaded union connector on each pipe near the rear- those pipes will need to be removed for future servicing. 

Actually, consider running both the hot and cold down the left hand wall, and elbowing horizontally into the WH inlets. I think that would be cleaner, and easier to access later for servicing. 

Where's the TPR valve on the new unit?

Im assuming that's what the galvanized pipe is coming over the old unit...

22 years old with galvanized used? 

Our seismic requirements are less and code requires hard gas pipe only to the heater.  We can't use flex lines. 

SV reX said:

That's the most ridiculous (new) water heater I've ever seen!  Some engineer should be shot. 
 

Yeah, that sound fine. Don't forget your shutoffs (use ball valves instead of the gate valves you've got). I would also install a threaded union connector on each pipe near the rear- those pipes will need to be removed for future servicing. 

Actually, consider running both the hot and cold down the left hand wall, and elbowing horizontally into the WH inlets. I think that would be cleaner, and easier to access later for servicing. 

Where's the TPR valve on the new unit?

Im assuming that's what the galvanized pipe is coming over the old unit...

It's because the heat pump is in the upper quarter of the shell. 

I have a ball valve for the cold side. I hadn't considered putting one on the hot side. We've literally never had to service the old one. It actually still works but I'm sure that it is on its last legs.

Originally I was going to run PVC down the the LH side. That sounds like a good plan. I just need a few more elbows.

The TPR is right next to the hot outlet. I'm planning to run CPVC straight down, wrapping around the bottom with a couple 45s and then going out the back wall on the LH side. There's a drain for the chiller that I will run out that side too. The AC unit is right on the other side of that wall and there's a drain a couple feet away.

Datsun310Guy said:

22 years old with galvanized used? 

Our seismic requirements are less and code requires hard gas pipe only to the heater.  We can't use flex lines. 

I've hated that pipe since we moved in. Just not enough to get off my ass an replace it. LOL!

I'll be capping that gas line off and hopefully never using it again.

CAinCA said:

Our house turns 22 this summer so we've been doing some renovation. We replaced our gas furnace with a heat pump system and we're in the process of getting solar installed. Our utility has a program where they will give you a $2000 rebate if you replace your gas water heater with a hybrid/heat pump unit. That basically covers the cost of the unit.

Not sure if you can double-dip, but the IRA put into place some significant rebates for various efficiency & electrification upgrades, including HP water heaters. That number ($2k) is the cap IRRC, so it might just be your utility facilitating the rebate. Either way, worth a gander.

Here's a website w/ a calculator if you're curious on what's out there. If you qualify as low/moderate income, there's even upfront payments to help facilitate these upgrades. 

How much money can you get with the Inflation Reduction Act? — Rewiring America

I've been eyeing a HP water heater for a bit and hope to replace my gas unit with one in the next couple of years. It's cool to see them gaining some traction. 

CAinCA said:

I have a ball valve for the cold side. I hadn't considered putting one on the hot side.

Putting a valve on the hot side is a code violation in my area, I'd confirm that for where you live.

In reply to stuart in mn :

Really?  I've never heard of that. 
 

What's the reasoning for that?

I did a little homework on this...

There are no prohibitions for a shutoff valve on the hot side in the national plumbing code. 
 

There are some local municipalities that have adopted prohibitions (I'm looking at you, Chicago), because they consider it a "closed system" which could over-pressurize if the TPR valve failed. 
 

...except it's already a closed system, because every fixture have a valve on it. Dumb law. 
 

The TPR valve exists for the safety concerns. Additional rules to try to avoid over-pressurization are dumb, but apparently do exist at some local locations. 
 

 I use valves on both the hot and cold. 

Fupdiggity (Forum Supporter) said:

CAinCA said:

Our house turns 22 this summer so we've been doing some renovation. We replaced our gas furnace with a heat pump system and we're in the process of getting solar installed. Our utility has a program where they will give you a $2000 rebate if you replace your gas water heater with a hybrid/heat pump unit. That basically covers the cost of the unit.

Not sure if you can double-dip, but the IRA put into place some significant rebates for various efficiency & electrification upgrades, including HP water heaters. That number ($2k) is the cap IRRC, so it might just be your utility facilitating the rebate. Either way, worth a gander.

Here's a website w/ a calculator if you're curious on what's out there. If you qualify as low/moderate income, there's even upfront payments to help facilitate these upgrades. 

How much money can you get with the Inflation Reduction Act? — Rewiring America

I've been eyeing a HP water heater for a bit and hope to replace my gas unit with one in the next couple of years. It's cool to see them gaining some traction. 

I will be claiming the 30%/$2k tax credit for the heat pump HVAC so I'll already max out the heat pump credit for the year.  I'll also be able to claim the full 30% credit for the solar system.

The only gas appliances we'll have left will be our stove, fireplace, and a gas grill. Our gas usage should be less than a therm per day. The solar system we're installing should produce excess power on most days. We'll be on net metering so we can get credit for our excess production and use those credits when we need to. Our electric costs should be close to zero (just the grid hook up fees ~$20/mo). 

Following with interest.

California is indeed an interesting place....

SV reX said:

I did a little homework on this...

There are no prohibitions for a shutoff valve on the hot side in the national plumbing code. 
 

There are some local municipalities that have adopted prohibitions (I'm looking at you, Chicago), because they consider it a "closed system" which could over-pressurize if the TPR valve failed. 

Yes, exactly.  As I said it's the situation in my area and isn't necessarily prohibited elsewhere, but it's something worth checking.

I hope modern electric hot water heaters are better than ours was.  It was awful.  Expensive to run and took forever to reheat.  

In reply to mfennell :

Yep. They are MUCH better. 

mfennell said:

I hope modern electric hot water heaters are better than ours was.  It was awful.  Expensive to run and took forever to reheat.  

This one is a hybrid electric. It has a 3.85 energy factor AKA the heat pump exchanges 3.85W of heat for every W consumed. It also has two standard electric  elements that it can kick on for higher demand situations. It's 65 gallons and soon it will just be the two of us. I think it will be fine. 

I've been trying to read up on code for this. Apparently, the TPR drain is supposed to be in the same room as the WH. The idea being that you're more likely to see a leak than if it was just plumbed outside. I'll probably just bring it to the LH wall and then straight down the front. I'll try to make it less obtrusive manner than the original setup.

I'm going to get the permit today. Hopefully they will have a handout that clearly explains the requirements. 

I'd like to use CPVC pipe for the TPR if it's allowed. It's rated for 90C and should be easier/cheaper to deal with than copper or galvanized pipe.  I'll have to see if the local plumbing distributor carries it though.  

What are the differences between PVC pipe and CPVC pipe?
My 24-year old house has some CPVC and it seems more brittle than expected.

You can't use PVC for hot water. TPR discharge pipes handle hot water. 

In reply to CAinCA :

Here's a checklist for TPR discharge piping:

TPR discharge piping

I talked to an inspector and he said plumbing out the wall was OK as long as the end pointed down. He suggested going straight to the back wall and then running pipe down the outside wall. He also said that CPVC was fine for this use.

In reply to CAinCA :

Read my linked article. There is more to it than just that it points down. 
 

The issue is avoiding scalding. It should point down, be piped to within 6" of the ground. If he's gonna let you pipe direct to the outside fine (but that's technically not correct)

(FWIW, I piped my own direct to the outside too)

we have 3 of these in different properties since 2014 

love them

only downside- furthest room away takes a while for hot water 

Checking out how the hybrid/heat pump water heater thing works the only issue I see is making sure that coil stays clean. Doesn't look like there is any sort of filter on them, so whatever dust or debris in the air will get sucked into it.