Debris when sumping tanks

[redbaron1982]

The main reason why I am starting this thread is the tragic accident of @Freddb34.

Every now and then, when I swamp my tanks I get some amount of debris. The attached pictures are from today. It's not always there, today's was more on the high amount of debris for instance, most of the times is lower or none at all.

My question is, is this normal? Should I take any actions? My airplane is a J model from 1985, no bladders, tanks seal several years. No seapage, more than one of the sump ports getting stained from a veeery slow leak.

[toto]

That’s more debris than I have seen in my own tanks. The most I’ve seen is two or three tiny flakes. The sample is normally completely clean.

I’ll be interested to hear from the mx experts whether any action is required. 

[MikeOH]

To be honest, that would freak me out!  I never get any debris. I’d be looking for cause and checking ALL downstream filters. I guess I’ve always been paranoid and even more so after Fred’s accident.

[Schllc]

I never saw anything like that before and it would freak me out too. 
those things could easily clog screens or filters. After seeing how the tanks are done, it’s hard to imagine pieces that large being left in the tanks,  it it doesn’t look like sealant either.  Did you have the tanks sealed?  Maybe a previous owner had bad patchwork done?
I’d want to flush the tanks at a minimum. 

I have gotten tiny particles every time I have ever stumped any of my tanks, and that is on all the 10 mooney’s I have owned, and about a dozen or more others I have flown. 
The first time I got nothing was after I had my tanks resealed. 
 

[redbaron1982]

Thanks all for the answers, one clarification, just in case, the first pictures are really zoomed in. I'd say the large particles are maybe 1mm or 2mm at most.

[N201MKTurbo]

Most likely some of your top coat is deteriorating. Not the end of the world. The pickup screens should get it. Do you collect samples from your fuel selector? If not, you might want to start doing that just to see if it is getting that far.

[Shadrach]

@redbaron1982

That amount of debris would not bother me in the least.  I know for a fact that I have a large lantern fly carcass floating around in my left tank. None of that stuff is getting through the gascolator screen. 

The tragedy of @Freddb34’s accident is that it likely had nothing to do with the debris he found in the tank and everything to do with something awry in the fuel servo.

Unless you fly and fuel your aircraft in a sterile environment, particulate is going to enter the fuel tanks over time.
 

[DCarlton]

In the 20 years I've owned my F, I can't recall ever seeing anything in the cup but water one or two times at most.  I installed bladders this past summer.  Here's a pic of my old fuel tank pickup tubes and screens for reference.  Needless to say, I was happy to have new ones installed.  Not sure what the J tubes look like; my new ones were perforated tubes pinched off at the ends (no screen; just perforated tubing).    

[Schllc]

I didn’t realize you had zoomed in so much. Ok, I wouldn’t be so freaked out by that but, those curled pieces are definitely unusual.  I’ve never seen anything like that before,  
nothing larger than a grain of sand.

[Shadrach]

4 hours ago, DCarlton said:

In the 20 years I've owned my F, I can't recall ever seeing anything in the cup but water one or two times at most.  I installed bladders this past summer.  Here's a pic of my old fuel tank pickup tubes and screens for reference.  Needless to say, I was happy to have new ones installed.  Not sure what the J tubes look like; my new ones were perforated tubes pinched off at the ends (no screen; just perforated tubing).    

Why did you have those tubes replaced? That seems like make work. They look serviceable in the picture, perhaps there’s something I’m missing?

[Ragsf15e]

I have had 2 Mooneys now and both I have seen “little grains of sand”.  The first Mooney had old tanks.  Not leaking but old.  It almost always had the sand.  The new one has newly done tanks (with a patch now).  It has much less sand.  I have always thought it was pieces of sealant.  In truth it’s probably smaller than sand, but similar.

[DCarlton]

1 hour ago, Shadrach said:

Why did you have those tubes replaced? That seems like make work. They look serviceable in the picture, perhaps there’s something I’m missing?

They came with the Griggs bladder kit.  All new caps, vents, drains and pickup tubes.  I kept the parts that I thought someone might be able to use.  

[Shadrach]

1 minute ago, Ragsf15e said:

I have had 2 Mooneys now and both I have seen “little grains of sand”.  The first Mooney had old tanks.  Not leaking but old.  It almost always had the sand.  The new one has newly done tanks (with a patch now).  It has much less sand.  I have always thought it was pieces of sealant.  In truth it’s probably smaller than sand, but similar.

I think it can be many things. Whenever I do a tank repair, I flush the tanks with high pressure water. It usually takes a few years for particulate to start showing in the fuel samples. This leads me to believe that over time a small amount of particulate from the surrounding environment accumulates in the tanks.

[Flyler]

My plane has been parked outside while I complete my training. I've been doing a lot of inspection, removed the belly panels, wing access panels, etc.  Every time a plane or jet rolls past me, I am blasted with sand.  So much so that I've become a bit paranoid about my ram air intake. I check it for sediment on preflight.

I imagine there's a decent amount of this sand, not to mention just regular dust and pollen, that settles I to the groove around the gas caps and falls in when you fuel up.  I was wondering if much could make it through the breather tubes, but that has to be a really small amount.

I am sure there is a really good, bloody reason why our planes do not have a paper or fine mesh replaceable fuel filter on the firewall.  Does anyone know?

[47U]

11 hours ago, Ragsf15e said:

I have had 2 Mooneys now and both I have seen “little grains of sand”.  The first Mooney had old tanks.  Not leaking but old.  It almost always had the sand.

When these little grains started showing up I was concerned.  They were soft, so I figured it was the top coat.  No tank work in my ownership starting in 2008.  No history of a full strip and reseal.  Not leaking, just one brown rivet and a couple screws with stains on the wing walk panel.  The gascolator and screens were clean, but I got paranoid.  I figured this wasn’t going to get better by itself so I got on the schedule in Willmar.  Problem solved, no more debris in the sump samples.

[Fritz1]

Drain tanks completely by removing quick drains, flush each with  a gal or two of avgas, filter out all debris, refill with avgas and then see what happens, I have owned two Mooneys, current one going on 6 years on a complete reseal, have not seen that much debris in any of my tanks, however, the pickup screens and the screen in the gascolator are designed to handle this amount and much more

[Vance Harral]

I'll put in another data point for "normal", though it does always bother me a little.

We bought our airplane in 2004, with original sealant (1976) plus a sealant repair from the prior owner.  Over the course of the next 20 years, we essentially never took a fuel sample that didn't have a small amount of reddish debris, which I always assumed was deteriorating fuel tank sealant.  Spoke with several mechanics many times about it.  All were unconcerned, due to the three filters between the tanks and the engine.  The pics above show the coarse pickup screen filters in the fuel tanks, which would definitely let the debris through.  However, the fuel selector screen and the fuel servo screen are very fine and will not let this size particle through.  Over the years we would find occasional bits of debris in the fuel selector screen when cleaned at annual, but not much, and I eventually decided most of the debris in the tanks must sit below the tank pickups in the unusable portion of the fuel, and not slosh up high enough to get pulled into the fuel lines.  What few bits did never made it past the fuel selector screen, as I never saw any of that stuff in the fuel servo finger screen.

We had the tanks stripped and resealed in January.  Ironically, we're still getting a bit of debris in our samples, but we know where it's coming from.  The shop that did the reseal work slopped sealant in the rib drain holes, just like you're not supposed to (see AD 85-24-03), and we made them hand-drill out every hole.  This resulted in little bits of sealant debris in the tanks that could not be 100% cleaned out even with best effort, so we've been enduring a slow, decreasing number of bits showing up in the fuel samples.

Anyway, both with the deteriorating tank sealant prior to the reseal, and the small bits of detritus after, we've been getting this stuff in our fuel samples for 25 years with nary an engine hiccup.

[LANCECASPER]

4 hours ago, Vance Harral said:

I'll put in another data point for "normal", though it does always bother me a little.

We bought our airplane in 2004, with original sealant (1976) plus a sealant repair from the prior owner.  Over the course of the next 20 years, we essentially never took a fuel sample that didn't have a small amount of reddish debris, which I always assumed was deteriorating fuel tank sealant.  Spoke with several mechanics many times about it.  All were unconcerned, due to the three filters between the tanks and the engine.  The pics above show the coarse pickup screen filters in the fuel tanks, which would definitely let the debris through.  However, the fuel selector screen and the fuel servo screen are very small and will not let this size particle through.  Over the years we would find occasional bits of debris in the fuel selector screen when cleaned at annual, but not much, and I eventually decided most of the debris in the tanks must sit below the tank pickups in the unusable portion of the fuel, and not slosh up high enough to get pulled into the fuel lines.  What few bits did never made it past the fuel selector screen, as I never saw any of that stuff in the fuel servo finger screen.

We had the tanks stripped and resealed in January.  Ironically, we're still getting a bit of debris in our samples, but we know where it's coming from.  The shop that did the reseal work slopped sealant in the rib drain holes, just like you're not supposed to (see AD 85-24-03), and we made them hand-drill out every hole.  This resulted in little bits of sealant debris in the tanks that could not be 100% cleaned out even with best effort, so we've been enduring a slow, decreasing number of bits showing up in the fuel samples.

Anyway, both with the deteriorating tank sealant prior to the reseal, and the small bits of detritus after, we've been getting this stuff in our fuel samples for 25 years with nary an engine hiccup.

What shop did your reseal?

[Vance Harral]

6 minutes ago, LANCECASPER said:

What shop did your reseal?

It was not the famous Wet-Wingolgists, but I'm not going to discuss it further here, for fear of being blackballed on potential warranty service as a result of public complaint.  I realize this will frustrate the community and accept it may make you think less of me, but it's what we agreed to in our partnership.  All I'll say publicly is caveat emptor, and note that the clogged drain holes were far from the only, or the worst problem.

If anyone here is actively working on scheduling a fuel tank strip and reseal, you can PM me for details.  But that's the best I can offer.

[PT20J]

12 hours ago, Vance Harral said:

I'll put in another data point for "normal", though it does always bother me a little.

We bought our airplane in 2004, with original sealant (1976) plus a sealant repair from the prior owner.  Over the course of the next 20 years, we essentially never took a fuel sample that didn't have a small amount of reddish debris, which I always assumed was deteriorating fuel tank sealant.  Spoke with several mechanics many times about it.  All were unconcerned, due to the three filters between the tanks and the engine.  The pics above show the coarse pickup screen filters in the fuel tanks, which would definitely let the debris through.  However, the fuel selector screen and the fuel servo screen are very fine and will not let this size particle through.  Over the years we would find occasional bits of debris in the fuel selector screen when cleaned at annual, but not much, and I eventually decided most of the debris in the tanks must sit below the tank pickups in the unusable portion of the fuel, and not slosh up high enough to get pulled into the fuel lines.  What few bits did never made it past the fuel selector screen, as I never saw any of that stuff in the fuel servo finger screen.

We had the tanks stripped and resealed in January.  Ironically, we're still getting a bit of debris in our samples, but we know where it's coming from.  The shop that did the reseal work slopped sealant in the rib drain holes, just like you're not supposed to (see AD 85-24-03), and we made them hand-drill out every hole.  This resulted in little bits of sealant debris in the tanks that could not be 100% cleaned out even with best effort, so we've been enduring a slow, decreasing number of bits showing up in the fuel samples.

Anyway, both with the deteriorating tank sealant prior to the reseal, and the small bits of detritus after, we've been getting this stuff in our fuel samples for 25 years with nary an engine hiccup.

How did you discover the holes were plugged?

[Vance Harral]

1 hour ago, PT20J said:

How did you discover the holes were plugged?

Visually.  It was on our checklist to verify at pickup.  Painfully obvious with just a flashlight and inspection mirror, given that one of the tanks was empty upon arrival.

As I said, this was not the only, or the worst problem with the work.  Caveat emptor: owners should always make and execute a checklist when picking up an aircraft after major maintenance.

[SKI]

I had some minor debris when sumping the tanks in my Cherokee and sometimes a very slow drip. Turns out it was the O-rings in the drains themselves. They hadn't completely failed but were on their way out. The Mooney ones are slightly different but I'd assume there's still O-rings in there. I changed both drain valves and the problem went away. Being that your tanks have recently been sealed I wouldn't think that's the source, although it could be. See if you can find a log entry on if the drains were ever replaced and if not that's also a possibility. 

[skykrawler]

Gats jars have 200 micron screens.

Gascollator seem to typically be 74 micron or 120 micron.

I can't find a replacement for my gascollator screen (Shaw, bought by Parker).

 

[Yetti]

in instances like this the easiest way to answer the question for FI people is "When was my Fuel Servo Screen last checked?"    Should be every annual per the Mooney list.    It's a little hard to do because of location.  

[LANCECASPER]

On 11/17/2025 at 8:28 AM, skykrawler said:

Gats jars have 200 micron screens.

Gascollator seem to typically be 74 micron or 120 micron.

I can't find a replacement for my gascollator screen (Shaw, bought by Parker).

 

Would either of these work?

https://www.aircraftspruce.com/pages/ep/gascolators/gascolatorScreen.php