Occasional water flow from relief valve

Old 04-21-10, 08:30 AM
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Occasional water flow from relief valve

We have a hydronic oil fired boiler that lets out water thru the relief valve maybe once or twice a year. We already replaced the valve and expansion tank. The issue is that the expansion valve pipe empties into a 10 gallon pail to catch the water but sometimes this overflows and we get water on the floor. There is no floor drain available so I was thinking of putting a sump pump in the bucket and run a hose outside from that. Sound ok?
Old 04-21-10, 02:05 PM
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Yes, you could do as you propose but wouldn't it be better to discover and take care of why it is happening in the first place? Safety valves do not just burp for no reason.
Old 04-21-10, 03:45 PM
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Really... your idea is to put a band-aid on it instead of healing the boo-boo.

There are generally only THREE things that will cause overpressure and cause the relief to open.

1. Expansion tank either defective (you put a new one on), IMPROPER AIR CHARGE on the tank (this can happen with a brand new tank if it's not checked before it's installed), or possibly an under-sized tank.

2. Auto fill valve (aka 'pressure reducing valve') defective (leaking through internally, you won't 'see' the leak until the relief valve pops), or improperly adjusted.

3. IF your system makes domestic hot water via a 'tankless coil' in the boiler, these coils can leak internally and over pressure the boiler system.

So, to diagnose the problem, first tell us what the pressure on the boiler gauge is reading and the temperature on the gauge when you took the reading. TWO reading please, one with the boiler 'cool', and one with it HOT.

And we'll go from there...

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