Steam Boiler Overfill

steamer99

My residential Weil-Mclain steam boiler keeps filling up with water.

Two service professionals have looked at the system.

The following has already been done:
1. Replace Automatic Water Feeder
2. Clean thoroughly the Low Water Cutoff Sensor.
3. Thoroughly check that the Low Water Cutoff and Automatic Water Feeder are working correctly together and injecting the proper amount of water.
3. Check all valves and piping for any leaks (none found) involved in the fresh water feed to the boiler.
4. Remove and clean pressure gauge pigtail

It seems that the fresh water feed input having a leak somewhere into the boiler can be ruled out.

If the main water valve into the boiler is turned off, the boiler operates fine and the water level does not continue to rise -- manually feeding the boiler as needed.

The only other source of water into the boiler is the return condensate feed.

All radiators have an incline towards their input pipe to facilitate condensate return.

The boiler is almost 20 years old.

The automatic water feeder worked correctly for many years and then the overfilling problem began suddenly -- without any changes to the system.

When the boiler stops (thermostat reaches set temperature) - the water level will start to rise -- one of the service professional said if the water is from the condensate return lines, the amount returning is excessive.

The two professionals could not determine a definite fix to the problem.

Any ideas on how to fix this water overfill problem is greatly appreciated.

KC_Jones

For the sake of discussion what water is in the boiler, gets turned into steam, leaves the boiler, then returns as water.

You can't have more water returning than leaves the boiler, all new water comes from the water feed.

The only other source could be a tankless water heater in the boiler. Do you have one of those?

If the problem does not happen with the feeder turned off, the problem most likely is a slow return. The wet returns can become plugged with sludge over time due to corrosion. I would suggest you need to flush the wet returns.

Post some pictures of your installation so we can see what kind of valves you may have to facilitate cleaning the returns....or if you even have any.

Also I would suggest the "professionals" you have been using don't know steam and just needlessly replaced your water feeder.

Where are you located? We may know someone in your area that knows what they are doing.

Jamie Hall

Presumably you have an independent shutoff valve on the automatic water feeder line? Perhaps you have a bypass valve for manual feed around the autofeeder?

Let's think about this -- it shouldn't be hard.

When the main water valve to the boiler is turned off the boiler does not over fill. When it is turned on, it does. Therefore there is a valve on the pipes from the outlet of that main water valve to the boiler which is allowing water to flow when it shouldn't.

Might be the water feeder. It should shut off when the water level is high enough, but perhaps it doesn't. The problem might be in the feeder itself, although you have replaced it (which may not have been necessary). The problem might be in the probe electrics. The problem might be in the wiring between the probe and the feeder. Or... is there another valve somewhere, such as a bypass around the feeder? Which might be leaking?

steamer99

Appreciate the feedback.

I have a separate water heater -- so no tankless coil.

I don't believe I have any valves facilitating returns -- should I have these? -- and where would they be located?

The return pipe is in plain site -- and goes directly into the boiler.

I was told the return pipes are located correctly on the basement wall at the correct level to the boiler.

The return pipes being clogged up was suggested as a possiblity.

I don't think I was ripped off on the Feeder -- the first service technician did some tests on it and it did appear not to be functioning well -- it was also almost 20 years old.

I am located in Queens, NY -- if you could suggest a good technician for this -- definitely appreciated - Thanks.

Fred

Are you sure the manual bypass water valve isn't leaking past the stop? Is it a Ball valve or the older style valve with a washer in it?

steamer99

The pipe coming from the bypass valve to the boiler has a coupling on it -- so that it was possible to unscrew the pipe and directly check if any water was leaking through the valve -- and no water was seen -- as a precaution, the valve was also replaced with a new one since the original one was also about 20 years old.

Jamie Hall

I hate to say this, but that water is coming from somewhere and if it keeps coming after an hour or two its coming from your water supply. There is no other possibility.

Playing with the wet returns etc. may be entertaining, but they are not your problem (unless, and I suppose it could happen, some clever person has hooked up a water supply line to a return somewhere... and it's leaking into the system... )

Try "find a contractor" on this site. There are a number of really good people in your area, and since this is fundamentally a plumbing problem any of them, whether steam is their thing or not, will be able to find it and fix it.

steamer99

The possible scenarios can drive one crazy. When the main water is turned off, the Feeder won't add anymore water -- so even if the condensate is returning too slow, the water level should not rise over time and and does keep going down.. When the water main in turned on -- the water level gets low too quickly because of the late condensate return -- and the Feeder adds additional water which is not really needed -- so when the condensate returns, the amount of water is increased over time. Does that sound possible?

The Feeder-LWC were tested and appear to be working correctly and not overfilling.

Possible leaks in the Feeder and Bypass valves were tested for and do not appear to be an issue.

With the main water valve on and the boiler running, the water level stays stable.

Soon after the boiler stops due the Thermostat ---- the water level starts to increase more than a little. The Feeder is not active.

acab1975

I had this happen to me last year, and the cause was either a dirty LWCO sensor or dirty water, or combo of both. I pulled the LWCO sensor out, cleaned it thoroughly, and then drained/refilled the boiler 2 or three times till I was confident the water was clean, and problem resolved.

I am not a pro, or even a savvy DIYer, by any means, but in an effort to save paying for more service calls, I'd try the following in succession, testing between steps before moving onto the next (cut power to boiler before each step):

- Drain/refill boiler a few times
- Replace the sensor only
- Replace the LWCO module

KC_Jones

steamer99 said:

Soon after the boiler stops due the Thermostat ---- the water level starts to increase more than a little. The Feeder is not active.

Need some clarity here. Are you saying when the boiler stops it is at normal operating level, basically the level it was at prior to firing? Then after that it rises to a level higher than before it was firing.

OR

Are you saying after it's done firing the water level rises and eventually ends up at the level it was at prior to firing?

On of those would be considered (mostly) normal the other is a problem.

Fred

It is very possible that that boiler needs to be skimmed. It may be pushing water out into the returns, the LWCO calls for water and when the heating cycle is done, the water in the returns plus the added water creates an over fill situation. Has any work been done to the piping or boiler that may have introduced oils into the system? Of course, it could also be a near boiler piping issue that causes the water to leave the boiler and then the LWCO calls for more water. A few pictures would help.

acl10

I installed a VXT water feeder and set it for 8 minutes so there is plenty
of time for the return water to come back even if its slow

Jamie Hall

The key question is -- and I sort of think it has been answered and perhaps I'm dense so I may be the only one not sure of the answer at this point -- does the water level stop rising in the boiler at some time after the boiler stops running, or doesn't it -- does it just keep on slowly rising and rising and rising.

A simple positive answer to that, one way or the other, will point to two completely different sets of things to look at. Some of the posts have been looking at this as though the answer were one way, and others the other way.

Clarification is needed.