Replacing plastic sheathing on water level probe

Equipment doesn't work? Troubleshooting? If you're handy, members can help.

#1: Post by table »

Hi all,

This is for a Lelit Mara PL62S.

In the process of troubleshooting a leak I removed the water level probe and damaged the semi-transparent plastic sheathing around the probe. It now won't reinsert into the white plastic hub.

Replacing the entire sensor is $50, and seems silly given that I've damaged maybe a few cents worth of plastic sheathing. Any idea how I can replace just the semi-transparent sheating/tubing?


#2: Post by jgood »

If that's a "Liquid Level Probe" -- I think it's $18 on Chris Coffee's site. That's the probe (one of two) that sets the water level in the boiler. Might be worth a call to CC to verify that it'll fit.

table (original poster)

#3: Post by table (original poster) »

Their page ( shows a probe that doesn't even have the plastic sheathing. I sent them an email though, hopefully someone knows how I can procure some of the plastic tubing/sheathing without buying a whole new sensor.

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#4: Post by cafeIKE »

Show us what the whole fitting looks like.

The CC probe is a 'standard' type that should fit most any Italian machine.

The bigger question is why did you pull it? If you descale regularly or use non-scaling water, the probe never need come out. The probe is merely a piece of stainless rod. They don't fail, the sensor circuit does. If the probe is so scaled as to be defective, that's the least of your worries.

table (original poster)

#5: Post by table (original poster) »

Here is the probe (outside of the nut fittings). You can see how the sheathing is crimped/ruffled from me trying to reinsert it unsuccessfully into the plastic housing/nuts.

I pulled it because my machine seems to be sputtering excessively from the vacuum break. I pulled the vacuum break and water level probe out to check for scaling and clean them. When putting the water level probe back together I basically destroyed the plastic sheathing.

Why do some images of water sensor probes not have a plastic sheathing at all? What does the plastic sheathing do?

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#6: Post by Nunas »

table wrote:<snip> Why do some images of water sensor probes not have a plastic sheathing at all? What does the plastic sheathing do?
I doubt it does anything much on your machine. The probe needs to be insulted from the boiler, which is grounded. If the fittings on your machine are plastic and seal well enough to the rod, that alone would be good enough. If they were metal, then the sheath alone would do it too. Your machine is akin to having a belt and suspenders :lol: The thing is, it's possible that if you were to remove the sheath, the rod would not have sufficient diameter to seal well enough when you tighten the plastic fittings.

table (original poster)

#7: Post by table (original poster) »

For now, I've cut the tubing in half to preserve a 1.5" section that is mostly intact. That allowed me to insert the probe with sheathing far enough to make a seal with the plastic fitting.

I just put it all back together and ran the machine to make sure it was sealed. It seems like it's okay.

If anyone has a lead on PTFE tubing that can be used on these probes let me know, I'd still like to replace it if I can find suitable tubing.

Now on to figure out why my vacuum break is leaking...



#8: Post by JRising »

table wrote: Why do some images of water sensor probes not have a plastic sheathing at all? What does the plastic sheathing do?
The plastic sheath does 2 things. It seals between the stainless steel rod and the teflon insulator (white part) of the probe that swells and holds the sheath and rod when tightened. Additionally, it repels water better than stainless steel, so that droplets of water will not cling to the side of the probe due to surface tension for any length of time and possibly leave behind trace minerals and eventually provide a path to ground that is not the true boiler level. Remember, the moment the steam valve opens, the surface of the boiler water is boiling madly at well over boiling temp. Everything in there is getting splashed.

A lot of pictures don't show the sheath because it is cut off to a much shorter length. Probes only wore sheaths down below the knees before the 1950s, it really doesn't need to be that long. just long enough for a water drop to not bridge across it and it has to be present at the tightening point of the teflon gland that tightens on the rod, as far as I can tell.

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#9: Post by cafeIKE »

As long as the boiler pressure holds, it's fine.

The vac break fails due to scale or failed seal.

See Vacuum Relief Valve O-Ring Repair vs Full Replacement? for a long life unit than can be rebuilt with a silicone o-ring. The one shown is 15 years old and still does not leak.

table (original poster)

#10: Post by table (original poster) »

Thanks! Just picked one up in case it helps with the leaking I'm seeing. Any link for compatible o-rings?