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EasilyFound
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Posted: Tue Jun 3rd, 2008 02:59 pm |
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I have a gas water heater by AO Smith. I believe it is a commercial water heater. Model # PGC100-230. It is 75 gallons, and was installed in 1995. I looked on the outside of the tank to find the BTU, but I could not find it. I did not find anything remarkable when I inspected the outside of the tank this morning. What should I be looking for?
I have gotten an estimate for a replacement of this commerical water heater, as well as an estimate for installing two 50-gallon residential heaters piped to allow one tank to service the building while the other is in repair if such a need arises. A third estimate was for installation of an indirect water tank to be heated by a newly-installed gas fired boiler.
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elenano
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Posted: Tue Jun 3rd, 2008 03:38 pm |
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You're right: You're not going to be able to see much with that heater. You can't see inside the burner chamber as you can with a residential tank.
I tried to find a spec sheet for on it on Smith's site, but couldn't. That's not unusual. They only list current models and model numbers change periodically.
I would have said, from the model number, 100 gallons, 230,000 Btu. I revise what I said before. While the heater might still be OK, opening it up to check the anodes would be expensive. Unless it is side-plumbed, which it's probably not, then the plumbing would have to be disconnected or cut to get the outer and inner cover off to get access to the anodes, of which there are probably four.
I would say 230,000 Btu is overkill for four units. Using two 50s in series would probably be cheapest.
Randy Schuyler
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EasilyFound
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Posted: Tue Jun 3rd, 2008 05:06 pm |
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OK. So it looks like the unit should be replaced, is what your saying, correct? And you are correct that two 50 gallons is less expensive than replacing it with one 100 gallon tank, about 17% less, at least from the one estimate I have now.
The other puzzling thing is that the AO Smith person I talked to on the telephone today said that my model number was a residential water heater, not a commercial water heater, which is how it was described by the plumber who gave me the estimate. The model number of my tank is not on the AO Smith website, as you say, but mines look identical to the drawing on the parts information sheet for models PGC 75/100 244 etc . . . The plumber who came out must have made a mistake.
Thanks for your time. This was very helpful.
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elenano
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Posted: Wed Jun 4th, 2008 06:27 am |
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I couldn't find the model number you mentioned, so I'm confused there. I can see how a plumber might think that any 100-gallon water heater was commercial. There is a place at about 75,000 Btu where residential segues into commercial.
Typically, at that point, if it has a cleanout hatch, it's considered commercial and it has a shorter warranty. If it doesn't, it's residential and has a more generous warranty.
I'm going to, as my friend Larry Weingarten says, cause some more trouble. Can you see one or maybe two hex nuts on top of your water heater? I could imagine that with a 75,000-Btu tank. And how is the plumbing connected to the water heater? A tank that size will have either one-inch or one-and-a-half-inch plumbing. Which is it? Measure it to be sure. Steel or copper? Flex lines or dielectric unions? If flex, what diameter the flex?
Now, you don't have to do any of this if you don't want to, but there is still a chance that you could save a lot of money and stay with your current water heater. If getting into the water heater is easy enough, it might be worth it to change the anode and replace the dip tube. Also, as a last thought, you may be able to peer inside the combustion chamber with a flashlight. Remove the inner hatch with pliers if the heater has just been firing. Tell us what you see. Just causing trouble, as somebody would say.....
Randy Schuyler
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EasilyFound
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Posted: Wed Jun 4th, 2008 12:24 pm |
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As it turns out, when I called the plumber who installed a new boiler last summer, and asked him to come out and give an estimate for installing a new water heater, he did not dismiss the idea of changing the anode and dip tube, and asked me to measure the space between the ceiling and the top of the boiler, so I'm going to measure that before I leave for work today. He did note, though, that the labor cost of the repair might make it uneconomical to do a repair rather than installing a new tank.
The link to the water tank I mentioned in my last post is here.
The pipes that carry the water into and out of the tank are 1 inch copper. I see a hexagon nut on the copper pipe connection to the pipe nipple and inlet tube (25 and 26 respectively in the diagram in the link a few lines above). The copper pipe connects to a hexagon nut and then there is more piping from that nut into the nipple and inlet tube, and it looks to me that that piping is also copper, but as I sit here maybe it is steel? Is that likely?
There also is about 21 inches of clearance from the top of the tank to the ceiling, some of that clearance is blocked by the piping. I fear that 21 inches is not enough clearance. Maybe I can use a flexble anode? Otherwise, they'd have to sever the tank from the pipes to tilt the tank and reconnect it? Is that what would be req'd?
Last edited on Wed Jun 4th, 2008 02:41 pm by EasilyFound
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elenano
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Posted: Wed Jun 4th, 2008 06:31 pm |
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Thank you for the link. It looks like what I call a light commercial tank, one flue, one anode, one-inch plumbing. From your description, the plumbing is joined with dielectric unions.
I think I'm going to defer to your plumber on this one, since he can best judge the difficulties and cost of service. I don't want to lead you down a path where you spend a bunch of money for nothing. Unions are always troublesome to disconnect, and you'd have to disconnect one to replace the dip tube.
There should be a steel hex nut visible on the surface of the top of the tank, or possibly under a plastic cap. That would be the anode. If the plumber could shut off the water and pull the anode out that 21 inches of clearance that you have, then you'd know if it was worth it to do anything else. If there is some metal up and down the rod, a new anode will probably keep the tank going. If it's just a plug, or bare core wire, or bare core wire with some calcium stuck to it, then it's better to get a new tank. Oh, and a flex rod can indeed be used in that amount of clearance.
I'm guessing that after a dozen years protecting a tank that size there won't be much left of it. But we never know till we see the anode. There are places around the country where anodes and water heaters last a lot longer than we'd think. There are four variables to tank life: how well the tank was made at the factory, water quality, use and temperature setting.
Hope that helps.
Randy Schuyler
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EasilyFound
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Posted: Thu Jun 5th, 2008 12:47 am |
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| There is no steel hex nut on top of the tank, either visible or under a cap. There are a couple of circle dents, but nothing in them.
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elenano
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Posted: Thu Jun 5th, 2008 06:34 am |
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If the anode or anodes are hard to get to, then taken with everything else, I lean against trying to service the tank. The union is going to be trouble. They always are. Usually, we cut them off and put something else in their place, but that plus the rest gets expensive and given the size and age of the tank, I'm reluctant to push it too hard.
Randy Schuyler
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EasilyFound
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Posted: Thu Jun 5th, 2008 01:22 pm |
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| Thanks again for all of your time. Based on your strong recommendation to service the tank, I had assumed that getting access to the anode and diptube was a relatively easy matter regardless of what kind of tank I had or how it was hooked up. But now I understand the factors to consider when deciding whether to service the tank, and the amount of labor that seems to be needed to service my tank.
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elenano
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Posted: Thu Jun 5th, 2008 05:55 pm |
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Most of the people who come here have residential tanks and those are relatively easy to service. Commercial tanks are another matter. If they're side-plumbed, they're a piece of cake, but a top-plumbed tank with unions and anodes beneath the cover can get messy.
That spec sheet shows one anode a little to the right of the cold plumbing, and that may be where it is, but the plumber will have to cut the cover to get to it -- maybe. If the Btu input on the heater is higher and there is more than one flue, he might have to take everything apart and that's very messy.
If you decide to go with another commercial water heater, read the Commercial section of the site for our thoughts on installation.
Randy Schuyler
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EasilyFound
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Posted: Fri Jun 6th, 2008 07:25 pm |
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My plumber just emailed me to say that he can replace the anode and diptube at a cost of about 39% of what it would cost me to install two new 50 gallon tanks based on the quote that I got from another plumber. (Am I allowed to quote prices on this board? Some boards of this kind prohibit the posting of that kind of information.) My plumber said he'd have to disconnect the tank and tilt it to do the repair. I had mentioned to him earlier about flexible anode rods, but he did not think he had enough clearance to do that. Can I expect the tank to last long enough after the repair to make a repair cost effective? My gut tells me to just install the new tanks, but I'm open to being persuaded otherwise. FWIW, the plumber recommended the repair over an install of a similar single tank unit. I did not ask him about the option of installing two 50 gallon tanks instead of one 100 gallon tank.
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elenano
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Posted: Fri Jun 6th, 2008 09:35 pm |
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My gut feeling goes with yours. If it were a 40-gallon tank, I'd feel better about it. The thing is that everybody uses the same size anodes, so you'll find a .75-inch-diameter anode in 20-, 30-, 40-, 50-, 75- and 100-gallon heaters, but the interior surface area they have to protect is drastically different. My guess is that the one anode in your tank is completely consumed and that a new anode will also be rapidly consumed provided the tank even survives.
If you can put in two 50s, you can also prefit them with a second anode and flush kit so they can be serviced and made to last pretty much indefinitely. The only other issue is one of flow. The 50s will have 3/4-inch plumbing, while your current tank has one-inch. It may not matter as long as everybody doesn't take a shower at once, but I thought I should mention it. As I'm writing, I'm thinking that actually you shouldn't put a second anode in each one, as outlet rods also restrict flow even more. So do the flush kits and make the plumber remove the hex anodes and replace them using Teflon tape. That way you'll be able to change them easily when the time comes (check them in five years).
On the other hand, if you stick with a commercial tank, try to find one with at least two anodes that have exposed hex nuts on top. Bradford White may make something like that. Hope that helps.
Randy Schuyler
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EasilyFound
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Posted: Sat Jun 7th, 2008 07:05 pm |
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My plumber recommends an indirect hot water tank as the most energy efficient way to produce hot water, but acknowledges that this option is the most expensive. He did say that if my coop wants to take the least expensive option without being too short sighted, that we should do the repair, even though we've reached the avg lifespan of the tank. He says that our usage was not very high for the size tank that we have (four units and 7 full baths), and that less usage compared to compacity results in a longer lasting tank.
He does not recommend replacement with two 50 gallon tanks, and recommends, if we don't go for the indirect, that we just replace with a single 100 gallon tank. If that is the other option, then the repair would be about 30% of the cost of installing a new 100 gallon tank.
Is there any way to estimate how long the tank will last if we just do a repair? As I've said before, but for the debris in the hot water line, I've got no complaints about the hot water, except that sometimes I've had little hot water if I am one of the last people to shower in the morning when everyone showers on a work day. I don't know if we'd have the same problem with a new tank and if that is just a problem capacity.
Last edited on Sat Jun 7th, 2008 07:08 pm by EasilyFound
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eleent
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Posted: Sat Jun 7th, 2008 09:46 pm |
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Hello: To answer one part of your question: How long will tanks last if you replace the anode/s. If you find a fair amount od sacrificial metal left on the old anode and you don't have high pressure or dirty combustion air, a tank can be made to last many years with timely anode replacement. If the existing rod is basically gone, there will be tank damage and it'll be a guess how well a new anode can help. Usually it will keep a tank going, but sometimes it is simply too late. Another thing that happens is the new anode gets used up quickly and needs changing so often that it doesn't make sense economically.
The condition of the old anode will give you guidance on what course to choose.
Yours, Larry
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EasilyFound
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Posted: Sat Jun 7th, 2008 10:50 pm |
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| Is there a way to figure out the condition of the current anode without opening up the tank? If they open it up, see that the anode is too far shot as you say, then I'm halfway through a repair job before realizing I need to replace the tank. Seems to me that is the worst of both worlds.
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elenano
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Posted: Sun Jun 8th, 2008 01:06 am |
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Not definitively. If you can look inside the burner chamber, as described under Know-how elsewhere on the site, you can at least determine if the tank is already showing signs of rust and water marks, but the anode is the key part here, and you're right that it's a bit of a gamble.
Randy Schuyler
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EasilyFound
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Posted: Fri Sep 26th, 2008 06:06 am |
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| UPDATE: Today my plumber installed a new AO Smith 100 gallon hot water tank. He showed me the old dip tube, which had disintegrated a lot. It was about 3 feet long and had a hole at the top. He said that he was surpised that the old tank had hung on for so long and had not started to leak yet. He also flushed the hot water line. All seems fine now. Last edited on Fri Sep 26th, 2008 06:09 am by EasilyFound
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elenano
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Posted: Fri Sep 26th, 2008 10:36 pm |
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I can't help but wonder about the dip tube. Most dip tube ARE only three feet long, or less. And the hole at the top is normal, an anti-siphon feature. Was it broken or disintegrated?
Randy Schuyler
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EasilyFound
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Posted: Sat Sep 27th, 2008 05:27 am |
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| Definately disintegrated. For some reason, I thought that the tube went the full length of the tank. In any event, half of what I saw was sheared off so that only half of the tube in diameter was left.
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