Boiler Pressure Relief Valve Leaking -- too much pressure
For the past month the pressure relief valve on my boiler has been dripping water whenever the boiler runs. I thought it was a defective relief valve but on closer inspection, I notice it only happens when the boiler has heated up and the gauge reads approx. 30psi. The relief valve is clearly working as designed. I've read that this can happen because of a bad expansion tank or fill valve but need a little help on this. Maximum temp reached after boiler heats up is approx 172F and max pressure is 30psi. I've never touched the aquastat so its setting has never changed. Expansion tank--I have one of those overhead 15 gallon steel tanks with just a gate valve on the bottom of it. The tank has no gauge or air valve or anything else to adjust. I turned off the valve going to the tank, drained the tank (far less than 15 gallons came out) and then turned the valve back on and let the water run into it ---I could hear it running for a few seconds. I know these tanks are supposed to be pressurized to 12psi---how would I do that? Doesn't the Taco pressure regulator take care of that for me or is it something I have to do manually at the tank? If there is air space in this tank, could incorrect pressurization be a cause for my over-pressurized system? Pressure Regulator Fill Valve: how can I tell if this is bad? It's a Taco model 329-3 which is supposedly preset to 12psi. I don't see a Schraeder type of valve anywhere on my system that would allow me to take a pressure reading like on a car's tire. Could it be something else that I'm not thinking of? Thank you for any help. My Specifications: -Boiler: HydroTherm model HC-145D-PV, installed 1997 -Propane fuel source, well water, single story house -Pressure Regulator: Taco model 329-3 -Circulator Pump: Taco model 0010-F2 -Pressure Relief Valve: Conbraco model 10-407-05 (30psi) -Aquastat: Honeywell type L8148E -Expansion Tank: Bell Gossett Hydro Flo 15 gallon steel compression tank 29.5 x 12 Hey Hollywood! Chances are you may not have completely emptied the expansion tank. When you drain it, it will create a 'suction' inside and not allow all the water out, much as when you put your finger on a drinking straw and lift it out of the drink... the liquid stays in the straw. You can try loosening the drain hose at the drain valve and this will sometimes allow air into the tank and break the suction... sometimes the only way to break the suction is to blow back into the hose ... but try not to get a mouthful of boiler water ... use a small compressor if you have one.... OR, your pressure valve is leaking through and pressurizing... OR, if you have one, the tankless coil for domestic hot water is leaking into the boiler and pressurizing... When you drain the tank and refill (it will fill with water to 1/2 to 2/3 full after draining, the 'air bubble' will compress) the pressure valve will pressurize it along with the rest of the boiler system to whatever the setting is on the valve. On a cold boiler, 12-15 PSI... If after you drain and reopen the valve, you see the pressure continue to climb past 15 PSI BEFORE the boiler is turned back on, that means that the pressure valve is leaking... and since you are on well water, it's very possible. So, try draining the tank again, and make sure ALL the water is out. Close the drain, reopen the valve to the tank, and keep an eye on the pressure to see that it levels off at 12-15 before refiring the boiler. Do you have a tankless coil for domestic hot water or a separate water heater? Hi NJ Trooper: Thanks for the helpful assistance. I have a separate hot water heater. I did as you suggested and you were right---there was still a lot of water in the tank. I let the boiler cool for about four hours before starting the job. Even with a siphon to push air into the tank's drain outlet, I couldn't get it to easily drain out. So, I just left the short hose sitting in a container while the water trickled and gulped air and after about 30 minutes, I had about 12 gallons emptied. I noticed though that the pressure gauge on the boiler was reading about 16-17psi when I started the job and slowly rose to 20psi during this whole process (with a cold boiler). After the tank was empty, I closed the drain outlet on the tank, opened the water valve to the tank and watched the pressure immediately drop to 0 and then slowly raise to about 17-18psi where it leveled out. I then fired up the boiler. The boiler turned off once it reached 180 degrees and 24psi. Much better than 30psi and a leaking safety valve. Thank you for solving that! But, does the 24psi maximum sound too high? Do you still think the cold pressures point to a bad pressure regulator valve? Thank you very much for your help. about 16-17psi when I started the job and slowly rose to 20psi during this whole process (with a cold boiler). Was this while you were draining the expansion tank, and with the valve in the line to the tank closed? does the 24psi maximum sound too high? No, not at all... IF it stays there! think the cold pressures point to a bad pressure regulator valve? If the cold pressure is STABLE then I wouldn't worry about it. While 16-17-18 is a little high, as long as the HOT pressure doesn't go above 25-27 PSI you should be fine. If you are A.R. like me, you _could_ adjust the regulator down a bit, but: If the pressure continues to creep up slowly, it would indicate that the regulator (aka 'pressure reducing valve') is leaking through. If you see this happening, let the boiler cool off some, and CLOSE the MANUAL feedwater valve. Open a drain and let some pressure off... say down to 15 PSI or so... leave the manual valve closed and run the boiler for a day or two and keep an eye on the pressures. If closing the manual valve keeps the pressure under control, then it's pretty certain the reducing valve is leaking. You can run the boiler this way until warm weather sets in and you have a chance to change that valve, but KEEP AN EYE ON THE PRESSURE! You don't want it to go too low either... Systems with standard steel compression tanks should NOT have any type of automatic float type air vents installed. You want the air in the system to find it's way back to the expansion tank, where it belongs. If you have any of these (they look like small brass 'cans' with a vent valve on top) screw the cap down tight. If you like, post some pictures of the system. We'll lookem over and maybe offer some other suggestions... free account / Image hosting, free photo sharing video sharing at Photobucket / upload there / drop link to album here. Hi Trooper, Was this while you were draining the expansion tank, and with the valve in the line to the tank closed Yes, this happened while draining the tank with the valve closed. Is this a concern? Since draining the tank two days ago, the pressure has been a constant 24 psi max while the boiler has been running. It's cold here so the boiler has certainly had a workout and not a drop of water out of the pressure relief valve. What do you think about the Bell Gossett DT-2 Drain-O-Tank for my expansion tank? DT-2 Drain-O-Tank Air Charger offers a sure, quick way to recharge a water-logged compression tank. I have several photos of my system posted on these two links: ImageShack® - Gallery ImageShack® - Gallery What is the in-line valve, just after the Taco pressure regulator? It says Walworth 125 on it but can't find anything searching for that term on the Internet. Could it be a backflow valve (I hope so)? Am I correct that those are air bleeder valves on the radiant lines in the living space? What is causing that white powdery material---calcium? or something from small water leaks? What you see accumulated over a couple of years. I want to insulate the basement boiler pipes (the basement is OUTSIDE of my thermal envelope). What do you think of using this type of insulation (see below link)? This particular insulation (and all other types like this I've seen) have a rating of 180F as the maximum temp (due to the strip of pressure sensitive adhesive on the insulation). The PexSupply page says 220F is the max but that is not taking the adhesive into consideration (I checked with the manufacturer). I'd feel more comfortable if the temp rating for whatever insulation I use is higher than 180F since the boiler is set at 180F. Do you know of pre-formed insulation (other than expensive fiberglass) that would have a higher rating and be useful for boilers? Armaflex Pipe Insulation - Copper Pipe Insulation - PEX Tubing Insulation - PEX Pipe Insulation Thanks for all the help. My boiler is getting more efficient by the day! -Chris Yes, this happened while draining the tank with the valve closed. Is this a concern? No, probably not. With the valve to the tank closed, there was no room for ANY expansion, and if there was ANY heat left in the boiler, that expansion would exaggerate the pressure increase... so what you saw is probably normal, given that you say the pressure is holding tough at 24 HOT. I don't know that changing the drain valve is really necessary. How often does it need to be done really? and how much trouble was it really to get it all the way empty? Your call... Could it be a backflow valve (I hope so)? Appears to be a 'swing check' valve. It IS a backflow preventer of sorts... though probably no longer 'approved' by codes as such. The ones they use today are actually DOUBLE check valves with an atmospheric vent in between. The one you have will still allow backflow if the disc inside doesn't seat 100%. The type most often seen these days is a Watts 9D. If you were on city water, I would say just leave it be, but since you are on well, you might consider a more 'robust' backflow preventer. Also, when/if you change that out, I would also suggest adding a 'wye strainer' after the manual valve, before the regulator. Use the type that you can 'blow down' with a drain valve. This will keep 'crud' from the well out of the regulator and backflow valves. Am I correct that those are air bleeder valves on the radiant lines in the living space? What is causing that white powdery material---calcium? or something from small water leaks? What you see accumulated over a couple of years. Yes, they are, and they appear to be the 'automatic' variety that I hate... there are 'discs' inside those that are hygroscopic and swell when they are wet which supposedly 'seals' the vent. When they dry because there is air behind them, they shrink and let the air out, then get wet and swell again. To put it bluntly, they suck. The one on the riser on the top of your boiler has a screw/coin slot in it, correct? That's what I would replace those with. Yes, the white powder is mineral 'salts'... and could in fact be salt... if you soften your water... also, it appears that the gaskets on the circ pump have the same deposits, and they are probably 'weeping' also. I usually just use that cheap foam plastic crap that HD and Lowes sells... it's not the best R value... but haven't had any trouble with the adhesive yet... it hasn't melted... if there is any other water piping down there, you might wanna think twice about insulating too much... you might want to keep SOME heat down there to keep other stuff from freezing. Hello, Don't want to hijack this thread, but wanted to say that it's been very informative. Last night I created a thread similar to this one regarding a leaking pressure relief valve when temperatures exceed 150єF. I am going to post some pictures of my setup in the other thread and hope for a little help. This is my first experience with boiler heat and I must say it's a little confusing. I was surprised to see that the main city water supply line goes in to the to-system manifold which leads me to belive this water can circulate throughout my home even before it goes through the boiler. But I wasn't really thinking about this as a selaed system without constant flow from the city water. Anyways, thanks for the indirect help... - Rich Thanks for all the help Trooper. Wye strainer - I'm a little confused by this component. I understand it has an opening that allows one to blow down the system. I guess that means opening it up and releasing any solids that may have accumulated. Without a wye strainer, those solids would go further into the boiler piping and might cause issues with other components----is that correct? How often should they be opened to release the junk that builds up? Can you recommend a particular make/model of wye strainer? I see that Watts makes these but not sure if they have the feature you suggested ---- type that you can 'blow down' with a drain valve. They all seem to have plugs you have to remove instead of a simple gate valve. There seems to be a drain valve on the Taco circulator pump. I've never opened that in the two years I've owned this house. Should that be drained regularly too? Bleeder valves - You mentioned I should change out the bleeder valves on my living space radiant lines with ones like the one in front of the boiler (yes, that one has a coin slot). I notice there are many varieties of these vents--Taco hy-vents, Varivalves, Watts vents, Hoffman, etc. Is there something specific I should be looking at for my system? This forum is a great resource and I'm glad others can benefit from each of the postings. How often should they be opened to release the junk that builds up? Kinda depends on how much stuff actually is in the water... you might not need it even, if the water comes off after a filter for example... you might be able to get an idea of this by removing a sink aerator, or washing machine hose and check the strainers to see how much they have caught. Since not much water moves along the pipe to the boiler, there might be more 'buildup' of 'stuff' in that pipe... so even just a valve ahead is better than nothing... something you can open and flush a few gallons periodically. The 'plug' can be removed and a valve installed. If you have a floor drain, you can route a pipe to that, or just use a hose to blow down. The strainer is also removable for cleaning if need be. Don't use a gate valve. Use a 'ball type' boiler drain valve. Brand? Watts is fine... there are others, they are all basically the same thing... There seems to be a drain valve on the Taco circulator pump Not sure what you mean... is this actually 'on' the pump? or on the piping near the pump? You probably don't have to do anything with that valve if it's what I think it is, unless you actually have air in the pipes that you need to purge out. Just looked at the pics again... you must be talking about a drain on the pipe near the pump, cuz all I see in the pic is a standard pump... Bleeder valves I also looked at the pics of the bleeders again... it looks like only that one is the automatic type, the others are the manual 'coin' variety... if they aren't leaking, as that one is not, they don't need replacing... the second one in the second gallery is leaking a bit and should be replaced. Some serious corrosion there! You might want to do some brushing and vacuuming on the fins in the baseboards also, you would be surprised how much more heat you will get out of them... doesn't take much dust to seriously affect the heat output. Stay away from the 'automatic float type' air vent. They can and do leak over time and you don't want something like that hidden inside a baseboard cabinet. I know they are made for that purpose, but I just don't trust them. A leak could go undetected for a long time. And, since you have a standard compression tank, you don't want any automatic vents on the system.
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