New shower... brown water!!! All copper and pex; what could the problem be?

We just replaced the tub/shower in a full bathroom renovation. Original supply lines were copper, and we never had this problem before. Supply lines were cut and redone with pex. Elbows are brass NPT/pex fittings. The shower nipple is brass; tub spout tube is copper. The new valve is a Moentrol single handle valve.

When the faucet is turned on, we get a couple seconds of brownish water. This occurs either at the shower or the tub (although the tub water looks darker).
Since it's coming out of both, we're suspecting the valve. Is that likely?

What could this be??? (And, how can we fix it?)

Thank you!

The most common problem is a steel pipe or fitting used in the piping. It is probably the pipe going to the diverter spout. When you use the tub, it comes out "full strength", but since the initial shower water has to go down to the spout, it dilutes the rust giving a lighter color.

HI, thanks for the reply. My DH is a marine plumber and he did the installation. He did not use any mild steel anywhere he's aware of... he's super conscientious about that stuff coming from the marine industry..... just PEX, copper and brass as described. We've been going over and over all the components used and trying to figure out what the cuprit is... it is VERY frustrating!!! We really want to figure it out since it's a major bummer -in a brand-new bathroom- to have scuzzy brown water

As stated, without a picture of the actual installation, there is no where we can imagine where a steel component would have been used, but there is NOTHING in the valve itself which could produce the problem. All its components are brass, rubber, or stainless steel. I hope you do NOT have a drywall screw, or nail, through a water line, which COULD produce that problem, at least until it rusts off and you have a flood. (I have had situations where it happened within a matter of weeks, and other times when it took many years before the "leak" appeared.)

Thanks... We can see all of the supply lines through either the access panel or up through the basement, no screws.
We've pulled apart the valve and there is significant rust in the "balancing spool" part.. we're rinsing it out and will pull the main cartridge to check it as well.
The Moen tech support have been great and although they clain there can't be any rust-able parts in there, they're happy to send us any replacement parts we need. Maybe we will find a bit if metal debris inside when we pull the cartridge.

Did you drain your hot water heater during the plumbing process? When I replaced my old galvanized lines with pex and installed a warm water recirculation loop I had to drain my water heater. On startup of the system we had some rusty colored water for almost a week. After about a week it was completely gone... just a possibility.

Update: when looking into the valve body, behind where the balancing spool goes, there are rust spots (see pic).
DH put a piece of green scotchbrite on needlenose pliers and can clean them off, but obviously he can't get everywhere. He's flushing it all out now, and Moen is sending us a new cartridge and balancing spool. The Moen tech said she can't imagine how the rust got in there in the first place (particularly since it's only been installed a few weeks, and in use a few days.) The valve came from a normal Moen dealer and was in perfectly pristine packaging, hadn't been sitting around under a dripping leaky roof or anything like that! So what's going on???

Moen offered to send a whole new valve, but replacing the whole valve would entail ripping out either the newly tiled shower wall or the opposite (old plaster) wall in the hall. Neither of which is in the least bit appealing.

Arrrgh!

arfeller, thanks.... We didn't drain the HW heater, but if it was that, wouldn't we see the same brown water coming out of the newly installed lav faucet as well? it's ONLY from the shower/tub. And we do see the rust inside the tub valve....

staceyneil said:

arfeller, thanks.... We didn't drain the HW heater, but if it was that, wouldn't we see the same brown water coming out of the newly installed lav faucet as well? it's ONLY from the shower/tub. And we do see the rust inside the tub valve....

Click to expand...

Drain and flush your heater until the water coming out is clear. Then flush your hot water pipes. Then if you still have brown water you'll have eliminated the heater.

It's a good practice to drain & flush water heaters once a year anyway so the job is probably needed if you haven't done that for a while. Also, maybe think about replacing the anode rod(s) in the water heater if you haven't done that in 5 to 7 years.

HRG

Hmmm. So you actually think it could be the hot water heater even though NO other fixtures in the house are affected? How could that be?

staceyneil said:

Hmmm. So you actually think it could be the hot water heater even though NO other fixtures in the house are affected? How could that be?

Click to expand...

When you redid your supply lines and then turned the water on to the water heater, the sudden volume of water into your heater may have loosened sediment at the bottom of your heater. That could be sent down your hot water pipes and accumulate at the output valve for your shower and tub because the higher volume of water has an easier time to move sediment along the inside of your supply line. Maybe not as much of a problem with the lower volume of water from faucets in vanity basins.

So maybe there's sediment accumulated at your tub/shower faucets which is causing the problem. If so, it would be good to flush the heater to reduce future problems. I would also remove the guts of the hot water faucet, shower head and any aerators in basin spouts and flush out the hot water line completely.

There are some videos on youtube that show what the brownish water looks like when flushing water heaters that have not been flushed for a while. Maybe you can compare what you're seeing with those videos.

Just brain storming here,
HRG

The rust in the valve could be a "result", rather than the "cause" if whatever is causing the rust, sent those particles into the valve where they lodged.