Indirect tank not moving much hot water

lbeachmike

I believe I have a bad expansion tank. I tapped on it and it just makes a thud - sounds water-logged.

Is this consistent with the symptoms?

1. hot water is being produced
2. seems the hot water is not being moved as it normally would be (tank outlet is hot at tank, but not much beyond) ... but ...
3. i'm not sure how to read the left side of the gauge on the tank

hot_rod

You have a reverse indirect, an older model, The tank, about 28 gallons holds boiler water
The 3 in the model number refers to 3 copper coils inside that hold the dhw

The tank in the picture is for the domestic water not the boiler water. Push in the air stem at the bottom quickly, air should come out. If water comes out the tank is done.


One of those green pumps moved boiler water into the tank to heat the copper coils

I would check the control and pump first, make sure it runs when the control calls for hot water

interesting control thermostat😗

lbeachmike

It's not the circulator. The pipe running from the circulator to the heating coils is super-hot.

I'm sure the expansion tank is done - just wanted a better understanding as to why a bad expansion tank reduces the water flow from the water tank to the fixtures. Thanks.

hot_rod

lbeachmike said:

It's not the circulator. The pipe running from the circulator to the heating coils is super-hot.

I'm sure the expansion tank is done - just wanted a better understanding as to why a bad expansion tank reduces the water flow from the water tank to the fixtures. Thanks.

It doesn’t. It is there to absorb the pressure increase as the DHW water temperature rises. It is only necessary if you have a backflow device or check valve on the incoming water service. When they fail, pressure goes up in the hot water piping. So you get high pressure when you first open a tap, then it tapers off. But that is not the intent of the tank😳

Are you on a well by chance?
.
Not much water capacity in those reverse Indirects, a smaller DHW tank would, a #5 ThermTrol. Pre charge pressure needs to be adjusted properly.

One other issue with those tanks. At the cold water connection at the bottom is an orifice/ restrictor plate. It limits the amount of flow through the copper coils. I have had them scale over, almost closed off. The symptom is good pressure for a few seconds, then it drops way off. Not enough opening to keep up with the hot water demand.

lbeachmike

That does not seem to match my symptoms.

How about, in the below, the gunked up bleeder valve? Can that cause any problems like this?

Or how about the thermostat shown in the pic?

hot_rod

Try turning the green knob on that mixing valve from on extreme to the other. They can lime up and stick in a cold or warm position. Or the temperature output fluctuates hot, cold, luke warm as a faucet runs.

With hard water they need to be cleaned from time to time. In some instances they need yearly service. The valve looks newer than the tank?

lbeachmike

To reiterate - there is no issue with the temperature of the hot water. If I turn on only hot water at a fixture, it is exactly the same temperature as always. But it is not the same volume as normal.

HVACNUT

lbeachmike said:

To reiterate - there is no issue with the temperature of the hot water. If I turn on only hot water at a fixture, it is exactly the same temperature as always. But it is not the same volume as normal.

Same temperature but less volume still leads to the mixing valve, or clogged aerators and shower heads. 
Get a 5 gallon bucket and run the hot from a tub into the bucket and time it.
The air eliminator on top of the tank could use replacing too.

psb75

The mixing valve is a mechanical device between the hot water coils and your points of service. It is highly suspect (see the lime scale on it?). Yes, start at the faucet aerators and shower heads and work backwards...to the mixing valve. And DO check the cold water inlet to the coils. Replace the air vent canister on top of the tank. A perhaps, replace a failed expansion tank.

lbeachmike

It's not the fixtures - that is easy to diagnose. All fixtures exhibit precisely the same symptoms. However, the symptoms are intermittent. Fine on Saturday, not fine on Sunday. This morning seems a ton better than yesterday - like wouldn't notice that there's an issue.

lbeachmike

I put a pressure gauge on the expansion tank and *nothing* at all happened. I pushed in pretty hard - no water, no air - nothing.

I rotated the mixing valve knob. Seems to rotate smoothly.

hot_rod

Some mixing valves have fine strainers on the hot and cold connections.
That would be one of easiest things to check.

If it is a flow volume issue, you have a restriction somewhere in the piping, connections, or valves

Grallert

With all that lime in the water could be valve stems on the hot side

hot_rod

This is a kit used to descale tankless water heaters and coils
That TurboMax is essentially a tankless coil

A plumber could  add some connections so you could flow this cleaner through the tank and the mixing valve

lbeachmike

How often would this need to be done? The tank has been there for 10-11 years.

Why do I see the scaley stuff even on the outside of soldered connections?

hot_rod

The minerals in your water have leaked out of a small hole in that soldered joint. Probably sealing off the leak.

You might want to have the hardness of you water checked. Hard water above 8-10 gpg or so is tough on all the plumbing components.

Simple test strips at the hardware store, or a dropper kit online.
Here is the water quality spec from TurboMax

lbeachmike

The strange thing is that we don't have hard water here. I leave near the beach. We have water tank water drilled from the third aquifer. I grew up with hard water and the water here is night and day. Across three different houses in this town over 30 years, I've never had issues with hard water deposits (like we did where I grew up.)

Re: potential issue with buildups causing flow restriction - this doesn't seem to make sense. If it were a buildup causing a flow restriction, that restriction would be constant - not intermittent. Don't you agree?

hot_rod

Have you tested the hardness? That white fuzz around the leaking copper joint indicates some mineral content. Same with the mineral build up on the brass air vent on the tank, although that is on the boiler water side.

An intermittent flow issue would take me back to a sticking mix valve. When the flow is restricted go down and feel the pipes going into the mix valve. Should be hot as the tank on the H port, cold as the incoming water on the C side. A strap on temperature gauge at the Mix port would show if the valve is regulating accurately also. If that temperature varies as water is flowing the mix valve is sticking. The outlet should not vary more than 2-3°

If that expansion tank is waterlogged, that often leads to the relief valve on top of the tank dripping or discharging. Although they can stick shut also. Have you noticed water coming out of that white pvc discharge tube?

Officially speaking that T&P relief valve may be mis-applied. The probe built into those valves should reach down into the tank. There are some extended probe versions but that looks to be a bit too much distance? But that is another issue.

As I see it, remove and clean the mix valve, check and clean the strainers on the mix valve if it has them. Replace the corroded air vent, check the operation of the pressure relief valve, actually I would replace that safety valve also, with an extended probe version. Replace the expansion tank, with a properly pre-charged one.

hot_rod

I wonder if that expansion tank was acting as a well tank. It holds 3 or so gallons of water at 60 psi line pressure,
 With a piping restriction it would allow that 3 gallons at 60 psi back into  the system if the pressure drops due to a restriction in the piping somehow .

if thus all started when the tank waterlogged that would explain it. The operating tank could be masking another flow restriction.

Its called fall off pressure in the pressure reducing valve world.

@Larry Weingarten might know?

Larry Weingarten

Hi, One more thing to look for is dissimilar metal connections. Where brass or copper join steel, it will cause the steel to rust and begin to restrict flow. I've seen where copper connections to a steel tank get plugged by the action of the anode in the tank. That said, I'd follow the flow path of the water and check things, one at a time, to see what's happening. A way to speed up the process is to run water from different places, like tank drain or tub spout to see how they flow. That should help guide you to the restriction/s.

Yours, Larry