Replacing water heater drain valve

I wanted to replace the plastic drain valve with a new metal valve after flushing the water heater. The old plastic valve was destroyed during removal, so I don't have it for reference. However, I am not having much luck getting the new valve to go in. I am suspecting that this is because the sludge might be partially clogging the threads. Although I carefully cleaned it and shopvac'd it, I still cannot seem to get the new valve in. It just would not even catch the first turn. However, if I use a new plastic valve instead, and force it hard enough, I am able to get it to go at least part way. For now I am sticking with the plastic valve but I would really like the metal valve. Any suggestions on what the problem might be?
BTW, the flush operation was successful. The heater is not making nearly as much noise as before. I had to use my shopvac with a small plastic tube extension and sucked most of the sludge from the heater. Simply running the water did not do the job. There must have been about one quart of sludge (texture of fine sand).
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Andrew Sarangan wrote:

There may be remnants of the old plastic valve stuck in the threads on the heater. Best would be a 3/4" pipe tap, but they're expensive for a one-off. Try a 3/4" cleaning brush (used for cleaning copper fittings). Alternate: grind a number of flats (lengthwise) on the threads of a 3/4" steel nipple; that will resemble the cutting action of tap.
I recommend using a 3/4" "heater nipple" between the heater boss and the new valve. I've had corrosion problems when a brass valve is screwed directly into the boss. And, if you use a galv nipple, there will be corrosion at the valve end. YMMV Best valve to use is a ball valve for full bore flow.
Jim
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
And if you use a ball valve, it will facilitate probing around in the tank to break up the crusted stuff.

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Stick with the plastic valve. It's a piece of shite compared to a good metal valve, but you won't have any galvanic corrosion problems with it.
If you want to use a ball valve for full flow like the Jim just suggested, get a plastic one, they're not uncommon. Like these:
http://www.specialtymfg.com/v1.htm
Happy New Year,
Jeff
--
Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"If you can smile when things are going wrong, you've thought of someone
  Click to see the full signature.
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
Jeff,
The concern I'd have with using PVC valves like these is that when used for sustained periods at elevated temperatures without operation they tend to fail when subsequently used. PVC is not usually used at hot water heater temperatures.
A good quality brass valve, even in a steel tank may corrode but the PTFE seats and seals will leave the valve able to be opened and closed when needed later. It may not be removable from tank but it's probably a good idea to replace the valve when the tank is replaced.
RB
Jeff Wisnia wrote:

Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload
RB wrote:

Excellent point, and I defer to your experience with aged PVC valves. I wouldn't have thought of that until it was too late.
But, it wouldn't be the brass valve which would corrode. its presence would just add to the galvanic corrosion of the steel tank near the drain port.
Think about it; Temperature/Pressure relief valves are all brass. Have you ever seen one of them corroded? If they did, you can bet the safety guys would have done something about it by now. It's the tank, always the tank....dammit...
Happy New Year,
Jeff
http://home.comcast.net/~jwisnia18/jeff /
-- Jeff Wisnia (W1BSV + Brass Rat '57 EE)
"If you can keep smiling when things go wrong, you've thought of someone to place the blame on."
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

Before I installed a new water heater I replaced the plastic drain with a galvanized one. The tank was guaranteed for 8 years and lasted 13. As stated above, the tank went before anything else. The drain had minor corrosion after those 13 years, but nothing signficant.
Enuf
Add pictures here
<% if( /^image/.test(type) ){ %>
<% } %>
<%-name%>
Add image file
Upload

HomeOwnersHub.com is a website for homeowners and building and maintenance pros. It is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.