Filter for outlet of water heater

Got a rather nasty sediment problem with my water heater. The stuff doesn't seem interested in coming out the drain, I've tried several times. But it happily will travel out into the rest of the plumbing system, clogging aerators, shower heads, etc.
It occurs to me that a simple solution would be to put a filter on the outlet side of the heater. But most filters I see have plastic housings and components and don't look like they'd tolerate the temperature.
Anyone ever seen a filter that would work in this application?
Yeah I know the "right" solution would probably be a softener on the inlet, but lack of space, money, and time pretty much rules that out.
Thanks!
Eric Law Wilmington, MA
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EL wrote:

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Well, I'm inclined to think it's not the pipes, the house is only 5 years old. And it's only on the hot water so probably not the supply.
Luckily it's a simple test: starting with a clean tub, I can run cold water in it all day and it stays clean. Run the hot full blast for a minute or two and you end up with a bunch of "sand" in the tub. We're on city water, and this has been going on for months so I don't think it's related to pipe flushing or anything like that.
Eric
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EL wrote:

Those are hardened calcium deposits.
The *real* fix for is periodic flushing of the tank. Do an Advanced search: http://groups.google.com / on this ng for: water heater draining (flushing) for gobs of ideas.
To get your 5 yr old heater draining again, you'll probably have to remove the drain cock. (Be prepared to handle the water that will come out.) Replace the factory drain with a 3/4" "heater nipple" and a 3/4" ball valve with a hose fitting on the valve outlet if you need to connect a hose.
Once you get the crap out, flush the tank under full pressure once a month. All you need is to get a bucket or so of water out each time. That keeps the calcium concentration low enough that it doesn't precipitate out.
Jim
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I think the problem is they are *stuck* hardened calcium deposits.
The drain valve works fine - I can get great flow out of it, but the deposits stay in the tank! I have actually removed the valve and it looks like there's only maybe 1/8" of deposits.
The heater is oil-fired (not off the house furnace, it has it's own burner) and makes "boiling" sounds when the burner is running. I think it's the "boiling" that breaks the deposits loose. I've tried running water out the drain while the burner's running but still get very little out.
I think the deposits are intelligent and malicious and *know* which way to exit the tank to cause the most trouble ;^)
Eric

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EL wrote:

Yes, an oil-fired unit can be very hard to cope with. I think you're right on all counts. If you ever have to replace it, a monthly blow-down may keep it clean.
As for filtering the Hot outlet, the best device I can think of is a "WYE strainer". Like: http://www.backflowparts.com/catalog/showProduct.cfm?vendorID &pageNumber=3
Watts makes them too and Cash-Acme (bought out/merged?) A plumbing supply house will have them and shouldn't be a big project to install. You might put a ball valve upstream and down to isolate the strainer for cleaning.
Jim

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Jim, Hey, thanks for the info! I'll check that out.
I must admit I had high hopes when we first bought this house - I'd heard stories about how much hot water you can get from an oil-fired heater. But doesn't seem like it's worth the trouble. And man, they're expensive to replace!
Eric Law

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