How to Clean a Steam Y Strainer

how to clean a y strainer

Steam y strainer – it’s the dark looking y to the left of the valve.

A couple months ago at work, we were having issues maintaining the proper pressure on one of the low pressure steam systems.  The cause, well one of the causes, ended up being due to a clogged steam y strainer.  Using some pics, this post is going to go over cleaning a steam y strainer.  There are a lot of factors actually in choosing how often to clean them, we probably aren’t going to get into that.  It’s just important that if you do operate a steam system with y strainers, keep it in the back of your head that you should do some preventative maintenance on them.

I’m not a home heating expert by any means but I believe I have seen y strainers on them as well, tiny little ones that look like sideways y’s.  Those should have preventative maintenance done as well.  They are easy.


Why Clean Y Strainers?

Having nice and clean y strainer baskets keeps your system happy, in your building, facility, boiler (they should have strainers before the feed water pump suctions (as should every pump.).), or home. When clean and doing their job properly, they improve the overall efficiency of that system.  That is why they are there in the first place, not to be a pain in the bottom to clean, but to reduce maintenance downtime later.

Like this night when we couldn’t regulate the low pressure steam system pressure.  Of course it was Friday evening too.

Safety First

Keep in mind this is a steam system you’re working on.  Don’t expect anyone to look out for your safety but you.  I’m guilty of it, taking shortcuts here and there, no I don’t always lockout tagout every single thing I work on.  But I do make sure I am safe because ultimately it is up to me to go home.

If you’re not comfortable working on steam, ask for help.  Like me and refrigeration, it’s almost foreign to me, working on it that is. Anyways, do what you have to do to isolate that portion of the steam system.

steam y strainers

You can see the y strainers inside the boxes. They make up part of the low pressure steam header.

It’s going to be hotter than the blazes too, the piping, probably around 300F.  One of your first steps in setting up to clean the y strainer may be placing fans directed at the piping and where you’ll be working. Gloves – wear them if you’re not a man.  You can’t feel nuts and bolts with gloves on.  Let it cool a little, as a steam guy your hands will toughen lol.  Turn it for a second, curse, rub your fingers on your pants, repeat and loosen.

Cleaning the Y Strainer

You see where the boxes are yeah?  That’s what we want to disassemble and clean.  First let’s shut off the steam.

Immediately next to the boxes, the bleached pink things, those are each an inlet isolation valve.  Close the one next to the strainer you’ll be taking apart.

Then, to the left, you see another bleached valve.  It’s bleached that color because it is so hot, like the embers in a charcoal. These are the outlet isolation valves.  Again, close the one down line from the one you are cleaning.

You have no isolated the y strainer and the regulating valve from the rest of the high and low pressure steam headers, remember, in this case, this strainer is on a steam reducing station.  On the far right, before the valve, steam pressure is 105 psi.  After the valve on the left, after it has been reduced, it is at 10 psi.

And more specifically in this case, the pressure reducing valve has another steam valve that senses steam header pressure down line, we’d shut that as well.


Next, you want to get rid of any excess steam pressure in the little trapped pocket you just made.

We do this by opening the drain on the y strainer basket.  Take out the plug, or off the cap, and slowly crack open that valve.  If you inlet and isolation valves are holding, pressure should be gone quickly and you’re golden.

If not, figure out what is wrong with your isolation valves before taking it apart.  You don’t want to get burned and blasted in the face cleaning a strainer basket.

steam wye strainer

The basket coming out.

I apologize for not taking a better picture, didn’t have this post in mind when taking the photos.  But after relieving the pressure, you will remove usually 4 strainer cover bolts.  Sometimes if these have sat for a really long time without being removed, loosened, it’s best to apply some penetrating fluid, tap around with a mallet to vibrate it deep, that’s what she said, and then take them out.

As the cover starts to drop the basket usually does too, but it may stick up inside.  It can stick for a few different reasons but usually the most hazardous is when it’s because of corrosion products.

The whole purpose for a y strainer is to catch corrosion products as the steam passes through.  It does this my making the steam make a hard turn through a basket with tiny holes in it.  The corrosion particles can’t keep up and drop out in the basket.  Good stationary engineers clean these baskets.

The corrosion products clog up the basket and can eventually really hamper steam flow as well as this maintenance.

For one, sometimes the clump of corrosion products can like drop on you.  Like you’ll be sitting there thinking it’s stuck and the next instant you’ve got a 400F lump of metal waste the size of a kitten on the back of your hand.

The other is when the corrosion has actually welded itself to the inside.  This is a nightmare.  Sometimes it’s easier to replace the whole strainer because you WILL damage the basket getting it out.

how to clean a steam strainer

Basket in hand, cover on floor.

Hopefully you get the basket out.  From there, it’s just a matter of cleaning out all of the little perforated holes.  Making sure steam can get it’s pretty little head through there at full speed with as little pressure drop as possible.  Losing energy in a clogged strainer eh?  See how it all ties in?

The steam making that turn already will lose some pressure.  You’re the steam.  You’re running full blast straight ahead.  Can you make a 90 degree turn and not lose any speed?  Nope, of course you have to slow down.  Running at a wall? Then turning.

That’s what happens to steam in wye strainers, piping turns and bends.  And every time it does, it loses energy, never to be regained again.

Pretty insane to think that something as trivial as strainer maintenance ties into Newton, Pascal.  And oh my god, how a good water treatment program ties into all of this.  Don’t get me started.

Take a wire brush to the inside and outside, run it under a faucet first or better yet, as you scrub it.  If you’ve got tough spots use an awl and try to poke or scrape the matter off.  Be careful too, for whatever reason, whoever makes the baskets, makes them out of the softest thing known to man, like baby bottoms in cotton, so be gentle.  Especially when you put it back together.

building engineering pm's

Keep coming, keep coming, don’t scald my hand.

Um, nearly every time I end up bending one end of the damned thing because it is not perfectly, and I mean perfectly, lined up in there.  Take your time with this part.  Make sure it is completely flush or deeper than the mating surface of your cover.

If there was corrosion damage inside the strainer body and maybe welding or pitting did occur, this can greatly impact how easy, OR NOT, it is to get the basket back inside all the way.  Yet another reason to do proper maintenance.

We’ll get into gasket cutting at a later date.  This one was about cleaning.


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