Water Heaters - Flushing/percolating issues

We bought this house 5 months ago, and our gas HWH is "percolating" (term from the FAQ). I'm sure the PO never flushed it, he didn't bother using the whole-house prefilter because, as he said, the sediment was too great and clogged the filter too fast, and he didn't like changing it that often (grr). It is pretty loud, but it is in the attic so it resonates well and sitting next to it with my hand on it, it doesn't really vibrate or shake. I tried flushing it, but the water flow is not great and the amount of sediment that came out is unimpressive (probably not a thimbleful).

Is this due to clogged up drain valve probably?

Is there anything that can be done at this point? If I use a lot of hot water and let it percolate, then open up the drain valve, will this help (loosened sediment from the percs?)

Is the percolation itself increasing the damage to the tank and creating a greater risk of leakage?

TIA for your opinions.
Mike

From what you say about the water and the noise it makes . Id say get a new one now. On a gas water heater. The flue goes up in the middle of the tank to heat the water . The water will built up like a stone around and on the tube there . Till we get what you have now. It also cant heat as much water as when it was new.

Usually these noises occur when a heater is getting up in age. Check its age. If your heater is old and located in an attic, I would seriously think about replacement. I leaking heater in the attic spells major disaster.

I appreciate your help. Does the percolation actually damage the tank or is it just a sign it is too old and will fail because of some other reason?

From deciphering the serial number I think it was made in 1996, thus quite likely has been here the entire life of the house. I'm 3rd owner so can't know for sure. Wife and I are probably going to replace it in the next week or so, we are considering going tankless. I'll do searches on the topic here, but if anyone wants to chime in on this thread or post a link to a favorite web page I'll definitely read those opinions.

There are also a couple nagging questions tangentially related to this topic (HWH and scale/sediment buildup) I hope people wouldn't mind answering if they know:

1) For CaCO3 and related derivatives to form from heated water the CO2 gas must be driven off as the water increases temp. Where does this CO2 go in the tank? Is there gas pocket space in there?

2) I always was told (and I think the empirical evidence is supportive of this?) that softened water is better for HWH, gas or electric, because of vastly reduced scale deposits. I have softened water and my 6 yr old tea kettle agrees (and once again, the PO didn't use the softener...). However, every pool or spa/hot tub owners manual, chem distributor, etc. will tell you not to use softened water in those devices because it will corrode heater elements and pump motors rapidly. They recommend adding CaCl2 to raise Ca2+ to 250-400 ppm. That's pretty hard water. Anyone know what the conflicting dichotomy is all about?

1. The rumbling noise you hear is because very large chunks of mineral deposits trap heat underneath themselves. The water actually boils locally, because the heat doesn't transfer up. That boiling and rumbling of the scale chunks is what you hear.

2. We are plumbers, not chemists, so you will have to figure out for yourself if there is CO2 and where it goes. But if you cut open your old WH with a sawzall after you replace it , you will certainly be able to see the mineral chunks.

3. Softened water has some residual sodium in it. I don't know what the ph is, or if it causes corrosion. Haven't heard about that. I know that RO filtered water does have a lowered ph and is not good for copper pipes.