Feed tank and boiler flooding

will smith_4

Dean-What type of water level control do you have? You mentioned that the fresh water feed valve is closed off-I'm guessing that's just a quick fill line for initial filling, and you've got a mechanical feeder with pump control/low water cut-off. That should still have a water feed going to it. Sounds like the feeder is open.

dean_25

Heard some hammering this morning before work and just assumed my zone valve had some cold condensate behind it...went to work, came home to a cold house. Boiler was flooded, and so was the feeder tank. What's got me perplexed is the fresh water feed has been completely shut off, and I've drained the system back to nominal levels twice over the last month or so, and yet I'm still flooding.

The pattern follows the weather...it seems to happen when it rains steadily. Could I possibly be taking on groundwater?

dean_26

Fresh water feed goes to the boiler feed tank only, there is no leveling on the boiler itself, just an M&M 150 for the feed pump control and high/low water cutoff. The feed tank has a float controlled fresh water valve in it, but I have a gate valve before it and it is fully off.

I don't have any underground returns...so I figured it has to be some sort of feeder issue despite the "closed valves"...but with all fresh water going to the feed tank and not the boiler, why would the boiler flood? For a 2 pipe, boiler controlled feed tank system to flood in the boiler itself, the flooding has to be coming back down the mains, no? Or will water push past the impeller into the boiler?

Regardless..if I'm not purposefully feeding any fresh water and I blow down my float weekly AND pull off gallons and gallons of water every few weeks because of flooding...where is this water coming from? I have had the fresh water feed shut off for over a year...

Unknown

vacuum

A boiler produces vacuum after it shuts off and the steam collapses. If that vacuum can't be relieved through the tank vent for some reason (zone valves closing is one reason; there are many) the boiler will pull water THROUGH the pump and check valve to satisfy the pressure difference. High pressure goes to low pressure.

The tank will replace the water with fresh water. If your tank feed is closed, it's still a mystery.

A tankless coil with a pinhole can overfill a boiler, too.

Just some ideas to look into.

Noel

dean_26

Aha! Zone valves...

OK, I see how the boiler can flood via the feed tank if both zones close down. A single room zone valve is about 80 feet from the header, the main is right off of the header and both are, of course, closed at rest. Man...I hate zone valves.

Doesn't solve the feed tank flooding as well, unless there is still some water coming through the fresh water feed.

No hot water coil in boiler (though using one to feed a radiant zone to replace that single room zone sounds really tempting...no more zone valves!).

Another flooding option...there is a leg of the main and return that goes somewhere outside of the house about 3' above the boiler waterline. I'm guessing there was a line to the garage at one point (I see a spot out there that may have been a radiator, capped lines and all). The main is closed via a gate valve, but the return drops right to the main condensate return. There could be a small break or pinhole out there somewhere that is letting groundwater in...especially if the lines go low pressure. I would assume the feed tank would be horribly fouled with sediment though...

Guess it's time to call a pro and get a flow meter on my feed line.

Unknown

another hunch

It's possible that one of your buried lines leaks, and the vacuum and water table are conspiring together and pulling ground water in through the leaking pipes.

Can you temporarily disconnect the feed water line, to rule it out?

Noel