Need Help! Low water shut off, Possible leak in slab?

I bought a one story home last December, built on a slab with copper in floor. The old Crown boiler was no good, so first thing I did was purchase a Buderus G115/4 and installed with a friend. We kept the same setup as the Crown, (pump on return towards boiler).

This season, I noticed I was having to fill the boiler daily as the low water shut off kept kicking it off. I closed the ball valve to the expansion tank, and turned on the ball valve to allow fresh water in to the boiler (closed loop system) and watched the water meter at the street. To my surprise, it doesn't seem to move over an hour's time. I know the meter works as it can detect a slow drip in a faucet. In the boiler room, there is a return manifold with 4, 1/2" valves, and one 1" pipe with no valve. The return manifold is the same minus any valves. There is also a closet about 15' away from the boiler room that had 4 1/2" valves feeding off of a 1" copper pipe. I figured they were clogged/leaking so I jacked up the concrete, and replaced one of them and left it exposed so I can see if any leaking occurs. They look good, so I then suspected the Airtrol on the old steel expansion tank.

When the valve to the expansion tank is open, water seems to fill up the tank, and never make its way back to the boiler. Therefore, I suspected this was the problem. However, I closed off that valve yesterday to the expansion tank, and about 4 hours later, noticed the low water shutoff kicked off the boiler again! I am completely stumped here..

I know that water should be pumped away from system, and am going to remedy that asap by moving the Grundfos pump. As far as air elimination, I put a Hoffman air vent at the highest point of piping on the supply line, several inches after it exits the boiler.

Could it be anything other than a leak in the floor somewhere??

 

The water has to be going somewhere, right?

Aside from the lwco tripping, if you were to close the valve that feeds water into the system, do you see the pressure falling?

You should not run the boiler with the valve in the line to the expansion tank closed!

 

The pressure doesn't really change. It is consistently between 15 (cold) and 19 psi. Pressure looks good, yet once again last night the lwco turned off my heat. Another thing I've noticed is that I have never seen water temp hit more than 140. It takes a long time to even get up to 130.

 

Something weird here...

If you are losing water, the pressure HAS to go down! How could it not?

I'm more inclined to think that your LWCO is malfunctioning...

but, I asked about the pressure... if it stays pressurized with the FEED WATER VALVE CLOSED... because if you have the manual feed valve open, and you also have a pressure reducing valve, then the system will maintain the water pressure... AND for that matter, the level...

So, I'm thinking you've got something else going on.

I know it's gettin' cold out and all, but you need to let the boiler cool, make sure the feed valve is closed, and watch the pressure in the boiler for a few hours or more... as the boiler begins to cool, it will drop some, but what you are looking for is to see if the system holds pressure, or will it drop eventually to zero?

What make/model LWCO is installed? Do you have the instruction sheet for it?

 

I think it's a Watchguard. I don't think it's malfunctioning, because the system does take on water when I open the fill valve, I will check the and see what the pressure is at when I get home, it has been off all day. Is it possible that it still had air in the system since it had been off since last March? I just don't recall having to add water daily last season.

So should I not be able to hear the water whishing through the pipes? The valves on the other side of the house make some noise..

Thank you for your help, I greatly appreciate it!

 

No... a properly operating hydronic system should be durn near silent...

GuardDog maybe?

So then how do you know when to close the valve, if not by looking at the pressure gauge?

I wouldn't mind being able to SEE the system... pictures might help... free account / Image hosting, free photo sharing & video sharing at Photobucket / upload pics there / place link here for us to view your album.

 

That's it, GuardDog.

So iI have spent the weekend checking the pressure guage and here is what I found:

-When cold, pressure is holding at 10psi.

-When I fill up the system, pressure goes up to about 15psi.

-Once boiler is cranking, it's about 18psi.

I let the boiler run its' course the other day, where it shuts off due to low water cutoff, and I didn't touch it for at least 24 hours, then I checked the pressure and it was still at 10psi... I don't get why it would hold at 10 if there is a leak? Then again, I don't know where all that water would be going if there weren't a leak. Any suggestions on what the best method is for finding a copper leak in slab with carpet?

 

Mark, how are you 'filling up the system' ? opening a valve or something?

Are you sure that you don't have a 'pressure reducing valve' that is holding the pressure at 10, and all the while adding water to the system?

Here's the bad news... when concrete is in contact with copper, the pipe slowly gets eaten... and begins to leak...

So let's say you somehow manage to find the leak (if there is one, and I have no idea how yer gonna do that) and jack out the concrete, and fix the leak...

How long before you have another... and another... and...

We really need to see some pics...