Boiler pressure too high


Old 09-20-16, 05:55 PM
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Question Boiler pressure too high

The other day I noticed that my boiler was dumping water out the pressure relief valve. Three years ago when this happened, the cause was a faulty expansion tank.

This time, I replaced the expansion tank (though I'm pretty sure the other one was still ok - when let air out of it to test it a small amount of mist came out along with the air that was likely just water vapor that was condensed... but I figured it was easy enough to swap out the tank)

I also replaced the hyvent (the old one was caked over with crud and didn't look like it was working) and then I finally replaced the SF1165 feed regulator.

I replaced the feed regulator yesterday morning with a new one I bought at a box store (the old one was bronze, the new one was cast iron but otherwise they were the same specs etc).

I had the system drained to zero pressure and then turned the water back on and it came up to around 12-15 lbs. After firing the boiler it got up to 25+... I was monkeying with it for a while and drained the pressure down to zero and got it down to to around 12-15 psi before I left for work.

I accidently left the burner off all day (it heats the water in our hot water heater, but we aren't using our baseboard heaters yet so it isn't used much during the day anyway) and when I came back the system was up to 30 psi and had released some water through the pressure relief valve.

I thought that the feed regulator I bought must have been defective so I went back to the box store to pick up another one - they were out (apparently there was a run on them yesterday, because at 6am they had 3 of them and at 9pm they had zero)... I picked up a different style Honneywell "DialSet" valve hoping that they were targeting people like me looking to replace a 1156 so they would have made it the same dimensions... but it isn't a perfect fit so I didn't install it (I'd have to cut a half inch of pipe and solder on a new fitting on one side to use it)

I went to FW Webb this morning and picked up a new bronze SF1156S (bronze with sweat on one side - same as the one I had before so I can re-use the nut on the sweat connection side) and installed that this morning.

Now is what's making me go nuts. The one straight out of the box is pre-set to 15PSI. I was suspicious that maybe someone returned a broken one to the box store or maybe someone screwed with the set screw in the store while monkeying with it so maybe it was just set up wrong - but the one from the supply house I would expect to have not been touched so should definitely still be pre-set to 15psi. I install it, turn the water on... and it goes to around 15psi... and then I come back ten or fifteen minutes later and it's up to 20psi after not firing the burner.

Same story - the thing creeps up to 30psi throughout the day (though today the burner was on and my wife was doing a lot of laundry etc so it definitely fired a fair number of times today)

I came home today and tried to adjust it by taking off the fill lever housing on the top and screwing it counter-clockwise a bit to try to reduce the pressure.

I got it down to 10psi but then when I wait around for a while it is back up to 20psi without me firing the boiler.

I'm going to do another test shortly where I get it to 14 psi and then leave it sitting with the fill line shut off and then come back in 10 or 15 minutes and verify that the pressure isn't somehow creeping up on its own.

The water pressure in my house is 50 psi from a well - the regulator should be able to handle up to 100psi and the previous one (same model) worked fine up until recently...

Is it possible that 2 of those Watts feed pressure regulators were bad right out of the box??? Should I just go cut the pipe to length and install that DialSet regulator (one really nice feature of the dial set one is it has a 1/4" NPT thread hole you can screw a pressure gauge in to verify the pressure. I've thought about installing a pressure gauge right after my fill valve so I can isolate it from the system and verify that on its own it is at the correct pressure... but if I was going to go to that much work I might as well just switch to the dial set valve)

So my question is - what should I look at or do next to get the pressure steady to stop draining out the PRV?
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Old 09-20-16, 07:34 PM
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It gets even MORE strange - burner off. fill line shut off. Pressure goes up!?

I turned off the burner AND the line to the fill valve. About a half hour later the pressure had gone from 10 to 20psi. That makes no sense. I drained it back down to 10 psi and left the burner off and the line to the fill valve shut off.

So... now I think that my water heater is leaking water into the boiler. I can't think of any other source of water that would cause this pressure build up.

That doesn't sound cheap to replace
Old 09-20-16, 08:30 PM
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Welcome to the forums.

Not the boiler pro here but sounds like an interesting problem.

I agree that the tankless coil could have a pinhole leak in it.
How old is the system ?

A few pictures of your boiler and it's piping is handy for us to use as a reference.

The replacement coils aren't too hard or expensive to replace. The coils look to be around $200. Maybe it's time to switch over to an electric water heater.
Old 09-21-16, 03:39 AM
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I'll put some pics up of the setup today.

Unfortunately it's not a tankless heater, it's an indirect water heater tank... And a big one (80 gallons)

Electricity here (Vermont) is pretty pricey - 14 cents per kWh so unless it's ridiculously more expensive to keep using the boiler or using gas somehow to heat the water I'd rather not switch to electric.

The system is 10 years old. We've been living here for 4 years.

The boiler used to be oil fired but we switched to natural gas when we moved in.

When we replace this tank, going to tankless might be an option since we have the gas line in the utility room and it would be easy to run a vent outside for one.

I'm going to start getting some quotes today. I think replacing the heater itself would be more work than I can take on myself.
Old 09-21-16, 04:48 AM
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Indirect water heater can also leak pressure into your boiler system. Can you turn off the feed to the indirect for a while, and watch the boiler pressure? Also, is your boiler gauge accurate? Steve
Old 09-21-16, 06:48 PM
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I'm pretty sure that the indirect water heater is what is leaking pressure into the boiler.

I had a friend who is more experienced come by and he was less sure that it was the water heater than I was (the heater _looks_ brand new on the outside... is only 11 years old... etc)...

I bought a pressure gauge that screws onto the 3/4" drain hose fitting. On the bottom pipe going into the water heater (labeled "Boiler In") there's a drain valve - I connected the gauge to that drain valve. I isolated the water heater by turning off two valves (on the send and return line to the boiler) and then the water pressure quickly (in a matter of seconds) climbs up to around 35psi

Then I un-isolate the water heater, the pressure drops down quickly as I assume it's feeding the pressure into the boiler.

When I take off the gauge only a very small trickle of water comes out. Similar to the amount of water that constantly trickles out of the my pressure relief valve (makes sense, doesn't it? water comes in, pressure either goes up or water goes out... no other options really)

I don't know for sure that my boiler gauge is accurate - but it does tend to be right on 30psi when the relief valve is trickling out so they are at least conspiring with each other. The boiler gauge does read slightly higher than the test gauge I installed on my boiler drain valve. I'll compare the two when the water heater is calling for heat next time.

Fortunately they still make this model water heater - so replacing it with a direct replacement should not be too terribly difficult. The model I have doesn't have an anode on it - but their new ones do list having a sacrificial anode in them to help prevent corrosion. I have a water softener so I'm sure that helped accelerate the demise of this one.

Oh well.

Anyone want an 80 gallon water heater, slightly used?

Here are a bunch of pictures of my setup...
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Old 09-21-16, 06:55 PM
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Why not replace it with a 40 gallon gas water heater ?
Old 09-22-16, 06:54 AM
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Why not replace it with a 40 gallon gas water heater ?
Good suggestion. Big-box stores have them for less than $400. Relatively easy to install yourself if you can make pipe connections. Plus, with a gas-fired water heater, you won't have to run your boiler in the summertime.

They will try to up-sell you a larger, more efficient model - resist that.
Old 09-25-16, 07:12 AM
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That's not a bad idea, but we do go through a lot of water in my house and I'm sure it will get worse when my little ones become teenagers.

I was able to get the same model indirect fired tank locally from a supply house. I called around for quotes on it - a couple had them in stock. One was about five hundred cheaper than another (I think the more expensive one has a reputation for "taking care of their full time guys" by charging a lot more for people who dont have accounts with them / aren't full time plumbers etc)

A plumber friend came by and helped me install it yesterday. (So I guess it maybe doesn't really count as "do it yourself" since I called in help? But I diagnosed the problem and was with him the whole time helping so maybe I get partial credit?)

The funny thing is after we got it all put together and went to fire up the boiler, the burner kept on not proving flame and going into latch up mode... The burner is a rental conversion unit from my gas company... They have 24/7 on-call repair that is available (they tell you "it's going to be $145 plus parts for after hours repairs" when you call them, I suppose to encourage you to schedule when they aren't paying overtime, but if the problem is with the burner unit that you are renting then the parts and repairs are free... )

The burner guy replaced the electrode and flame sensor and cleaned it up. Still didn't work. Then he replaced the carlin controller thing and that did the trick. (This is the second time in 4 years that carlin controller thing has gone bad and been replaced...)
Old 09-25-16, 09:30 AM
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So don't leave us hanging....did it fix the pressure problem?
Old 09-26-16, 05:43 PM
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Yes, it fixed the pressure problem.
Old 09-26-16, 05:46 PM
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Good to hear, thanks for the update!

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