When I power off my GS/3 (ser. no. 296), water slowly drains from a boiler (I don't know which one) into the water reservoir. The following photo shows the water level when I powered off (the arrow/top of tape) and the level when I took the photo ~8 hours later. When the machine powered on the next morning, the boiler filled and the water level returned to the top of the tape.



The arrow is significant. After 3 days away with the machine powered off, the reservoir overflowed (I was ready for it with towels around the machine). When I returned and powered the GS/3, the boiler refilled and the arrow marks the water level afterwards.

Until the issue is diagnosed and repaired, I know I'm safe from water on the counter if the water level is not above the arrow when I turn off the machine.

I'd appreciate any and all help diagnosing the problem. Is there a one-way valve malfunctioning? Is it the pump?

Cheers,
John

My guess is that you have a bad check valve on the tea water mixing unit. This could be allowing water from the steam boiler to slowly leak back to the pump, and from there to the reservoir.

I don't think the water is coming from the coffee boiler because there are at least three check valves in the path, and there's no autofill function for the coffee boiler -- only the steam boiler has that.

But the mystery here is why the leak/overflow only occurs when the machine is off. I'm going to guess that the steam boiler actually does leak when the machine is on, but when the water level falls below the level probe, the autofill comes on and tops it off. Do you hear the pump cycle every now and then when the machine is on for a long time?

If the pump doesn't come on during operation, then I would speculate that the faulty valve expands a bit when the machine is warm and closes off the leak. When the machine cools down, the valve parts shrink slightly and the pathway is open. Seems like a long shot, but I've seen gaskets do this. But my bet is on the machine autofilling during operation, and that's why the reservoir level doesn't rise.

Peppersass wrote:My guess is that you have a bad check valve on the tea water mixing unit.

Thanks for your help Dick!

I called Chris Coffee and the tech I talked to is sure it's one of the check valves. They were out of stock and suggested I call LM to get the part quicker.

I called LM. The tech there, like you, believes the water is coming from the steam boiler. He's also sure it's one of the check valves. He suggested I start with the check valve at the pump. I'll do that since it seems easier to change. (#5 on p. 16 of parts catalog v2.3: http://www.lamarzoccousa.com/wp-content ... 3COLOR.pdf )

Perhaps both the check valve at the pump and the tea mixing unit would have to be stuck to get this behavior. The LM tech also said one can often clear the problem in the check valve. I'll try to clear it, but I have two valves coming and won't attempt a fix until they arrive.

Cheers,
John

Glad I could help (and hope I really did!)

Just out of curiosity, what did the check valves cost? Last I looked at the price from a dealer, they were something like $50 apiece.

Peppersass wrote:Just out of curiosity, what did the check valves cost? Last I looked at the price from a dealer, they were something like $50 apiece.

IIRC, $51. UPS delivery is tomorrow.

Well, I finally got around to replacing the check valve. Alas, I don't have a check valve at the pump!

Furthermore, I'm going to have to swap out a part in order to install the check valve.

The part to be discarded is the following (sorry for the out of focus photo, but I've already reinstalled it):


So, I'll have to call La Marzocco or Chris Coffee on Monday and wait for the additional parts.

On the plus side, it's an extremely easy procedure as it is quite accessible. I didn't have to drain the boilers (possibly because of the problem I'm having where it's already partially drained). I just removed the hose and taped it to the steam wand to keep it high.

While I'm at it, I'll see if I can get the longer hose to reduce vibration. Anyone know if the longer hose is the following part number?
L307 S/S FLEX TUBE GS/3 - CM 55 - NSF

Cheers,
John

After I posted my last comment, I got a private message from Chris at La Marzocco. At his request, I gave him a call and he explained that their are now seven check valves and we talked about which I should replace. I ended up getting five of the new [better spec'd] check valves, washers, the longer hose, and the new two-piece copper pope from the steam boiler to the mixing block (which is one of the new places for a check valve).

I received the shipment from La Marzocco today.

I added the check valve at the pump and installed the longer hose here:


...installed the two-piece copper pipe with new check valve here:


and replaced the two check valves at the mixing block:



I fired up the machine after and found no leaks. With two check valves in the way, I don't think I'm going to see any water flowing back into the reservoir.

I wanted to replace the check valve at the flowmeter also, but stupidly forgot and reinstalled everything. Oh well, I have the valve for the next time I do surgery.

Cheers,
John

I'm afraid that I have the same condition. Mine is an old machine with no check valve on the pump. I got as far as trying to remove the valve at the tea water mixer to see if it looked clogged, but I can't get the valve to budge, and was starting to damage the brass. Unfortunately, the part on the pump that needs to be discarded is also on so tightly that I fear removing it.

It's not a problem as long as I don't fill the reservoir right before turning the machine off for the night. Otherwise I wake up to a puddle under the machine.

--Matt

Hi Matt,

mgrayson wrote:I'm afraid that I have the same condition. Mine is an old machine with no check valve on the pump. I got as far as trying to remove the valve at the tea water mixer to see if it looked clogged, but I can't get the valve to budge, and was starting to damage the brass.

I followed the steps in the following thread to replace the check valve at the water mixer. Have you tried that?

La Marzocco GS3 massive water leak through OPV [resolved]

mgrayson wrote:Unfortunately, the part on the pump that needs to be discarded is also on so tightly that I fear removing it.

Mine was on tight also. I put a pipe wrench on the pump to secure it in place while removing the part. As I recall, I needed to snip a tie holding some wires in order to do that. I replaced the tie when I was done.

mgrayson wrote:It's not a problem as long as I don't fill the reservoir right before turning the machine off for the night. Otherwise I wake up to a puddle under the machine.

That gets old. Even if you just add the new check-valve at the pump, your problem should go away.

Cheers,
John

jakline wrote:I put a pipe wrench on the pump to secure it in place while removing the part.

I looked to see if I took any photos of that, and found a couple.