'Depressurization' Smell to Water ???

Every time we take the water pressure down in our house (which happens too often) we get a smell (and taste) to the water lasting for about a whole day. It happens immediately after bringing the pressure back on. What is this smell? I've asked plumbers and a water treatment 'expert' - their explanations are unsatisfactory.

The smell is sort of a stale air, musty smell but it's not what I would call earthy. It's certainly not a 'rotten egg' smell.

We have our own well (six years old) and high iron content in the well water. We have an iron filter (air injection system) and water softener. Both the softened and unsoftened, heated and unheated water has the smell.

The smell is not that bad but the taste is really annoying. Showering in that water causes you to taste it for a long time afterwards.

Does anyone know what would cause this? I'm convinced it has something to do directly with depressurizing and/or re-pressurizing the water.

Do you have a presser tank?
Have you flushed?

Yes, have a pressure tank and backflushing doesn't seem to be part of the equation. It smells for a day afterwards whether we backflush or not.

You mention that the smell is present on both sides of the heater and softener. What about the iron filter? Basically you've got to track down where the smell originates and then fix/alter that component. In other words you've got to sniff water samples taken ahead and below each device/appliance in the water system. Start working with the existing taps and add taps/drains as necessary to collect the required samples.

Yeah CHH, I can do that but it would take some effort. I have no convenient outlet to check before/after the iron filter itself to isolate it.

The thing is, this ONLY happens when the pressure gets taken down to nothing and then back up again to normal (40 - 55) pressure. I can't believe no one here has experienced this or has heard of it. The smell NEVER happens without taking the pressure down and ALWAYS occurs immediately after I do. So that leads me to believe that even if I would check before and after the different elements of the system I may not find the source. I think the source is a combination of whatever is in the water throughout the entire system and then the depressure/repressure process.

The contamination has to originate somewhere. It may be the well or it may be an appliance. If the smell is present at all points in the system then the source is the well.

The source has to be determined in order to solve the problem. Don't get hung up on the symptoms, just use them as a guide.

I'd turn off every angle stop in the house (to isolate each fixture)and then with the pressure down, turn each one on until you get your smell.

It's not uncommon to have a buildup in the inside of the pipes...when you cycle the pump off, that initial surge of water can dislodge some of the accumulated crud...happens on municipal systems, too when they flush the lines by opening a bunch of fire hydrants.

methodical process, even if it feels like trial and error, it will uncover some new data. As CHH said, the real problem is deeper than the fact that pressure went down to zero and back up; that was a trigger for the problem to "present itself". I repeat: pressurizing water is not a taste changer, and depressurizing water also is not a ... ... -- The activity was a trigger for another problem to become apparent.

After a few months, your thread will have been viewed by more than just a few people, so you may get a real good tip, one day, but not on Day One. Stay here and keep telling us more as you do more to diagnose the real problem.

David

Yeah, I'll try to check in. Have a few years of rust/iron buildup in the pipes I'm sure.
It IS interesting how the smell only occurs after the pressure release/restart but you're probably right - that may release some crud in the system exposing... whatever to cause the smell.

Right now we're enjoying actually having our iron filter (seem to) work for the first time in years. The air injector (small black inlet valve for those familiar with it) has not been sucking in air for a long, long time. I believe I know why but that's probably another thread. Now it works. And I think it'll take a LONG time for some of the iron deposits in our piping to gradually run through the system if they ever do.

Thanks for the responses. We'll see where this goes.

Okay, finally figured this out (if anyone cares).

Our house has in-floor heat in the basement and garage. We also roughed in a zone in a patio which we just started closing in. When the plumber was hooking up the final piping to get that zone added - and opened up the in-floor piping to top up the anti-freeze - we smelled 'that smell' again.

Turns out the smell is glycol (antifreeze for the in-floor heating system). The regular water system is supposed to keep the in-floor heat piping system at 15 psi pressure through a valve. Evidently when we take the pressure down in the water supply system the back-flow valve is letting some of the glycol escape back into the house water system. It then comes out of the taps when we use the water.

So that explains the smell and why it only occurs when we take the water pressure down to zero.

If you are using "glycol" in your heating system I sure hope it is food-grade Propylene Glycol. Ethylene Glycol (the kind usually used for automobile anti-freeze) is extremely poisonous.

In either case, if you are chemically treating your heating system (anti-freeze counts) then you need a reduced pressure backflow preventer between the heating system and the potable water system. The double check valve type of backflow preventer normally installed on hydronic heating systems does not provide the degree of safety needed.

Thanks Furd, I'll check. I know it has some sort of backflow valve but don't know what kind. I DO know it evidently wasn't doing the job properly.
And I don't know what sort of glycol the plumber put in but will check that too.
(Could that explain the sixth toe on each foot I've grown since this started happening?)