Drain W-M storage tank

Reino

My W-M indirect storage tank Gold PLUS 60 doesn't have a drain for the inner (domestic water) tank.  To periodically clean out sediment I hook up a low pressure air compressor to a hot water tap (sink faucet) open the cold water tap, and blow out the hot rusty water through the cold water faucet.  Seems to work OK; am I missing anything?

EricAune

Not really

This is the problem with tank-in-tank indirects, IMOP.  I have not tried the air method but if its working then you're in business.



I have installed an isolation ball valve on the outlet side (before the thermostatic mixing valve) and also a standard boiler drain.  Flush tank with incoming cold water, drain through added boiler drain valve.  Simple, but works too.

Jean-David Beyer

I am just a homeowner.

I have thought about this, but have not done it yet. The way my W-M tank is instaleld, ther eare three water ports on the top of the unit. One is the cold water input (no doubt with a dip tube to near the bottom), the hot water output with a long stem PT valve in it, and a third one with a dip tube. This third one can be used with recurcalating systems, or as a drain. There is a boiler drain valve on it. One way to drain the tank would be to turn off the cold water input, open a hot water tap, and use the third port to siphon the water out.



Another way would be to not open a hot water tap, turn on the cold water supply, and have that force the water out.



None of these ways, yours or my two, seem entirely satisfactory. But my old electric hot water was not either. It had a plastic drain valve that never sealed very well, so it leaked even if I used two washers. And I do not know if it was close enough to the bottom either.



Maybe there is a good reason to buy cheap tanks and replace them often. ;-)

Charlie from wmass

You need to watch that you do not

over stress the tank with pressure. Make sure the air is not set high. The third port is suppose to be how you drain the tank. It is suppose to have a dip tube in it with no relief hole in the side. Cold water dip tubes have a hole drilled in the side to prevent siphoning the water from the tank. I say suppose as some times it is removed by the installer to use that port for the T&P valve. If you have a vacuum relief on the inlet you can just hook up a hose start the water flowing and then close the cold water valve. Walk away and come back in a while and refill the tank.

Steamhead

How about

installing a sediment filter on the incoming water service? This will keep the sediment from getting into the tank in the first place.

meplumber

Huge Problem IMHO

We winterize a large number of summer homes here on the coast of Maine and it never fails that we have one or two a season that we just can't get to drain.  Air works but you have to be careful.  A tranfer pump works sometimes.  I hate them.  They are good tanks, but are a huge PITA.

Mark Eatherton

How DOES one winterize one of these beasts....

If memory serves me correctly, you MUST fill the inner tank BEFORE you fill the outer tank to avoid collapsing the inner tank. Unless the hydronic side of the DHW tank can be physically isolated, and the heating water depressurized, you are taking a chance on collapsing the inner tank, no?



Their installation instructions show an external low point drain connected to the cold water line going in to the top of the tank. Only problem is, that by code there is supposed to be a hole drilled at the top of the cold water inlet dip tube to act as an anti siphon feature.



So, when you try to drain it using the siphon method, it lowers the water down to the inlet breaker hole, then loses siphon and quits drawing. The ONLY way I've been able to do it is to slip a hose inside of the cold water inlet, lowering it all the way to the bottom of the tank, and siphon or vacuum the water out. Not a well thought out design IMPO.



ME

jp_2

tanks crushing?

sounds like failure waiting to happen?



that would suggest that if ever one side looses pressure the tank would fail?



since the domestic side is way higher in pressure than the boiler side, I would think the tank should be able to handle normal operating pressures with the other side empty or pressure less?



otherwise if either side had a pressure drop, the tank would fail.



heres where the BIG warning stickers would need to be.

Jean-David Beyer

Would that handle the sediment due to hard water?

I do not have the answers, but it seems to me that the major source of sediment in my indirect tank within a tank hot water heater would be the scale that deposits on the inner wall of the inner tank. Presumably this inner tank expands and contracts during normal operation (not much) and the scale breaks off and settles to the bottom. A filter on the water input would help only if there were sediment in the supply water, or if it could remove the dissolved salts (of calcium or magnesium, I suppose).

Jean-David Beyer

The instructions with my indirect are pretty clear.

They say to fill the domestic tank first before filling the outer tank.



My (former) contractor did not do that. They filled the outer tank first, so say there was 15 psi outside. And perhaps there was 45 psi inside after it was filled. This is a W-M indirect that is the same as someone else's (Triangle Tube?). It does not seem to have hurt it, but I was upset while they were doing it. Serves me right for reading the I&O manuals. They said it was how they always did it. Well, maybe they did.

jp_2

don't misunderstand

I don't dispute the installation manual...... But, doesn't it make sense that the tank needs to handle a condition where the boiler loose pressure or the domestic side loose pressure without failure?   especially if the boiler looses pressure and the domestic is over 60psi?

Jean-David Beyer

What "makes sense" to me may not reflect reality.

It seems to me that the design of the W-M indirects (and the Triangle Tube ones that are cosmetically a little different) is such that the inner tank (like a concertina)  should be able to resist high pressures inside. The higher the differential pressure on the inside tank, the longer it would get, but pretty soon it hits a limit, the bottom of the outer tank.



Now if there is no pressure in the inside tank, and 15 psi in the outer tank, this would tend to compress the concertina, and nothing stops it. So it might tend to compress it too far and break dip tubes, crease the "folds" of the concertina, etc. I do not think it would actually implode the inner tank. But I did not design that thing, so I do not know the actual failure modes.

ABSolar

Draining tanks

Hey fellow plumbers,

Page 1 in the Triangle Tube indirect water heater manual says "always fill inner tank prior to outer tank AND always drain outer tank prior to inner tank.  Relieve primary system pressure below 15 psig PRIOR to draining inner tank". 

The Triangle Smart tank IS the same thing as a Weil Mclein indirect tank (Triangle make 'em).  Options to drain the tank are siphoning, sucking with a pump, or blowing it out with an air compressor.  It IS unfortunate that there is no low point drain, but the expansion physics of a tank within a tank preclude a drain port that passes through 2 walls simultaneously, when that inner tank expands and contracts (movement) differently from the outer tank.

I think JDB is correct about the bellows type inner tank configuration not having a resistance to crushing from outer pressure, but the tank Can expand without damage.

As far as mineral scaling, there are several antiscale filter systems available to reduce/ eliminate water heater particulate build-up.  Cuno makes one that requires a phosphor pellet filled cartridege.  Watts makes a different system that makes the particuliate matter bond bond to itself in the micro stages of formation, and then just pass through the water heater without further bonding to tank walls, fittings and pipework.

The Triangle tank is probably a very good method of heat transfer compared to coil in tanks (surface area is greater).

AB