A water heater expansion tank is a crucial safety device, often required for homes with closed plumbing systems (built after 1985), that prevents excessive pressure buildup, pipe damage, and leaks by absorbing expanded, heated water. These tanks often last about 7 years, and are usually required when installing a new water heater.

I'm no plumber, but perhaps your installation is more complicated than it needs to be. Not sure why there is a valve shut off.

I am not a plumber by any means either. No home expert either - that is why I ask for opinion , but in comparison to elsewhere I have seen these, this appears more complex to me

The tank appears to be unsupported. Perhaps I can't see a bracket connecting it to the wall. The combination of PEX and csst is circuitous and unnecessary. Using copper directly out of the water heater as shown in the other photos can provide needed support for the expansion tank.

The shut-off valve should have been on the other side of the expansion tank. You want to be able to shut off the valve and replace the expansion tank. You also want to have expansion capacity for the water heater if you shut off the valve. As it is now, if the valve is closed and the water heater is still on the expanding water has no place to go

jumping in from the Ontario side. I see this quite a bit in the GTA where we’re retrofitting new tanks into older, tight mechanical rooms. It definitely looks like a "creative" afternoon for whoever installed it!

Jake The Wonderdog hit on the most critical point: that shut-off valve is in a very risky spot.

In Ontario, our plumbing code is pretty strict about "closed systems." Here is the breakdown of what I’m seeing from a pro perspective:

1. The Valve Dilemma (The "Safety" Issue)

The expansion tank's job is to act like a lung for your water heater. When water heats up, it expands; the tank gives that extra volume a place to go so your pipes don't burst or your T&P safety valve doesn't start leaking.

The Problem: By putting the shut-off valve between the water heater and the expansion tank, someone could accidentally close that valve while the heater is running. If that happens, the expansion tank is "cut off" and can't do its job, which puts a lot of unnecessary stress on your tank and home plumbing.

The Fix: That valve should be moved so the tank always has a clear, "un-valved" path to the water heater.

2. Support and Stability

Expansion tanks are light when they are full of air, but if the internal bladder ever fails, they fill with water and get very heavy (about 20–30 lbs).

Looking at the PEX and flexible lines in your photo, there isn't enough structural support. Over time, that weight can cause the plastic lines to sag or the fittings to leak.

In a professional Ontario install, we usually use a galvanized wall bracket or solid copper strapping to make sure that tank stays put, regardless of how much water is inside.

3. "Circuitous" Piping

You mentioned it looks complex - you’re right. Using a mix of PEX and flexible connectors creates a lot of extra "joints." In plumbing, every joint is a potential leak point. Ideally, this should have been a much straighter run of solid copper or a more direct PEX connection.

My Advice:

Since this was likely done to meet current codes during a replacement, I’d suggest having a licensed plumber come back to:

Relocate that valve so it doesn't accidentally isolate the safety tank.

Secure the tank with a proper wall-mount bracket so it isn't hanging by the pipes.