Any plumbers here? Howling water system and expansion tank killer.

[Sideways]

Obviously you lost pressure over the years. The most likely ways to lose it are a tiny leak in the schrader valve or a split in the rubber diaphragm in the expansion vessel. To be fully confident that the expansion is holding pressure, you need to take pressure off the hot tank before measuring it.
I'd give it a few days and do that routine again. Cheers.

 

[sploo]

Just checked again - the expansion tank was measuring 3.3 bar. I closed the valve on pipe A, ran a hot tap until no more water came out, and the expansion tank then read 2.9 bar.

I opened the valve back up, checked I'm getting hot water from the tap again, and a final check of the expansion tank still read 2.9 bar.

So it appears to be holding some pressure; though pipe A still howls when taps are run.

 

[Spectric]

though pipe A still howls when taps are run.

Can you record the sound as it might just help ?

 

[sploo]

Can you record the sound as it might just help ?

Sure. This is from a few weeks ago (not that long after it'd started). You can hear the water running, but also the howling noise. The pitch isn't always the same; right now if I run a cold tap it's a slightly higher frequency.

 

[Spectric]

Well that is a strange sound, not howling but more like a whining bearing or some worn out motor. It will need some thinking as it is not any form of water hammer as the frequency is much higher. Is there any vibration on the pipes that is in phase with the noise ?

 

[Bingy man]

I can’t play the sound for some reason but @Spectric mentions a motor or bearing. So I’m wondering if this system has a hot water return pump that is either faulty or incorrectly installed or both - just a thought . If it does pump valves could be the issue..

 

[sploo]

I'm reasonably certain it's pipework rather than a motor. The mic on my phone doesn't seem to pick up the frequencies very well (it seems to supress the howling noise a bit, and allows you to hear the water flow - at least more than I experience it in person).

I just ran a cold tap upstairs and got another video. The left pipe is A (cold water feed in, coming from downstairs), the middle is pipe B (cold water serving taps upstairs). There's definitely the most vibration (by feel) in pipe A. I can also eliminate the noise by reducing the flow in pipe A.

I then (not in the video) ran some hot water. There was no noise for a few seconds, and then it kicked in. My assumption is that some hot water is drained from the main cylinder, and when it realises the level has dropped it takes cold water from pipe A to refill the tank. That would again suggest to me that the problem is with pipe A (i.e. noise only when there's flow in pipe A).

 

[Spectric]

My assumption is that some hot water is drained from the main cylinder, and when it realises the level has dropped it takes cold water from pipe A to refill the tank. That would again suggest to me that the problem is with pipe A (i.e. noise only when there's flow in pipe A).

Having had a rethink, the one item in the feedpipe to the cylinder is the pressure regulator, I cannot see what make of valve this is but looks to be a Altechnic but they all work along similar lines. Now your pressure regulator is there to ensure a constant pressure supply to the cylinder and a supply to taps and mixers at the regulated pressure, it will also incorporate a one way valve to prevent backflow from the cylinder into the supply. Now what I cannot understand is that the cylinder has a built in pressure relief valve that discharges into the tundish, why is there another pressure valve on the water supply to the cylinder from the pressure regulator ? The pressure on the supply is the same as the cylinder water pressure so what is it there for ? You say pipe A is vibrating but listen to that pressure regulator and see if that is making any noise or vibration.

There should also be another expansion tank and excess pressure relief valve on the loop from the boiler to zone valves but that should not have any effect on your current problem, it is not shown in the picture.

 

[Jake]

Why is the ball valve at the bottom of A nearly in the closed position ?

Edit: in first pic, I see it is fully open in the video above.

 

[Jake]

Can't really make out what is going on the top, but that looks like it could be a whole house TMV at the top. If so, we had one of those for a while: ours was very noisy in a shrieky way, so we got rid of it.

 

[sploo]

Having had a rethink, the one item in the feedpipe to the cylinder is the pressure regulator, I cannot see what make of valve this is but looks to be a Altechnic but they all work along similar lines. Now your pressure regulator is there to ensure a constant pressure supply to the cylinder and a supply to taps and mixers at the regulated pressure, it will also incorporate a one way valve to prevent backflow from the cylinder into the supply. Now what I cannot understand is that the cylinder has a built in pressure relief valve that discharges into the tundish, why is there another pressure valve on the water supply to the cylinder from the pressure regulator ? The pressure on the supply is the same as the cylinder water pressure so what is it there for ? You say pipe A is vibrating but listen to that pressure regulator and see if that is making any noise or vibration.

There should also be another expansion tank and excess pressure relief valve on the loop from the boiler to zone valves but that should not have any effect on your current problem, it is not shown in the picture.

If by "the one item in the feedpipe to the cylinder is the pressure regulator" you mean the grey/red unit at the top left of the original photo, then yes, I'm pretty certain it's a Series 533002 CST (combined PRV and cold fill monobloc) by Altecnic.

Just to be obstinate, the pipework isn't howling this evening; though I had earlier drawn a lot of hot water from the tank. Next time it does I'll try to work out if it is the valve rather than the pipe.

 

[sploo]

Why is the ball valve at the bottom of A nearly in the closed position ?

Edit: in first pic, I see it is fully open in the video above.

Yea, I happened to take that picture while I was "experimenting". Reducing that valve does lessen the howling noise (but not always).

 

[Jake]

If it isn't clear what I meant this thing with the white knob at the top appears to have hot and cold going into it if I am following correctly (which may well be wrong) and hot coming out of it.

 

[sploo]

If it isn't clear what I meant this thing with the white knob at the top appears to have hot and cold going into it if I am following correctly (which may well be wrong) and hot coming out of it.

Pipe A is the cold in (from downstairs), pipe B is cold out (to taps and toilets upstairs), pipe D is also cold out - to refill the hot water cylinder (and it also goes to the expansion tank). Pipe C is hot water coming out of the top of the cylinder; the angle of the original photo perhaps doesn't help. Here's a shot from a slightly different angle that might be better.

I think (in answer to one of Spectric's earlier questions) that pipe E is the overflow/safety both for the cylinder being over pressure (the red valve at the right of the image below) and the safety for incoming cold water being too high pressure (the red valve at the top left of the image).

The grey knob (left of image) is the pressure reducing valve for the incoming cold water. The PRV manual describes the connection for pipe B as a "balanced take off".

 

[Sideways]

Now what I cannot understand is that the cylinder has a built in pressure relief valve that discharges into the tundish, why is there another pressure valve on the water supply to the cylinder from the pressure regulator ? The pressure on the supply is the same as the cylinder water pressure so what is it there for ? You say pipe A is vibrating but listen to that pressure regulator and see if that is making any noise or vibration.

There is supposed to be a temperature and pressure relief valve directly through the tank wall set at 7 bar, and another one paired with the pale grey Altechnic style monoblock valve. That one is set to let go at a lower pressure than the T&P. And they do share the same tundish and discharge pipe in the model layout.

I don't see anything fundamentally wrong with the pipework or combination of valves. Layout is a little different but it's just the same as on my own new tank which was installed per the manufacturers instructions and "model" layout.

Valve is installed roughly level with the top of the HW tank to minimise drain down when the valve has the be serviced or replaced.
Cold water mains is coming into the grey valve vertically downwards from above.
Balanced pressure cold water is going out to the shower mixer valve etc horizontally from the grey valve (bottom leg of the T if you picture it rotated 90 degrees)
Regulated feed into the tank is going vertically downward. In mine this pipe has a T off it where the expansion vessel connects
You can see both pressure relief valves (red) sharing the same discharge pipework from just above the tundish (lagged because these pipes, although empty, conduct heat from the tank and waste it).
The bottle trap you see automatically vents a high spot in the hot water heating coil which would tend to collect air.


Although the sound is said to be coming from pipe A in @sploo 's installation, I'd bet money that the actual source of the noise is vibration / resonance within the monoblock valve. A is just where the sound gets out.

 

[sploo]

There is supposed to be a temperature and pressure relief valve directly through the tank wall set at 7 bar, and another one paired with the pale grey Altechnic style monoblock valve. That one is set to let go at a lower pressure than the T&P. And they do share the same tundish and discharge pipe in the model layout.

I don't see anything fundamentally wrong with the pipework or combination of valves. Layout is a little different but it's just the same as on my own new tank which was installed per the manufacturers instructions and "model" layout.

View attachment 185187

Valve is installed roughly level with the top of the HW tank to minimise drain down when the valve has the be serviced or replaced.
Cold water mains is coming into the grey valve vertically downwards from above.
Balanced pressure cold water is going out to the shower mixer valve etc horizontally from the grey valve (bottom leg of the T if you picture it rotated 90 degrees)
Regulated feed into the tank is going vertically downward. In mine this pipe has a T off it where the expansion vessel connects
You can see both pressure relief valves (red) sharing the same discharge pipework from just above the tundish (lagged because these pipes, although empty, conduct heat from the tank and waste it).
The bottle trap you see automatically vents a high spot in the hot water heating coil which would tend to collect air.


Although the sound is said to be coming from pipe A in @sploo 's installation, I'd bet money that the actual source of the noise is vibration / resonance within the monoblock valve. A is just where the sound gets out.

Yep - that looks pretty much identical to my set up; other than your PRV block is the version with the optional expansion tank connector (black plug) on the bottom of the PRV block (right side in your orientation). The model I have has the optional plug on the rear.

I think the suggestion that the noise is coming from the PRV valve likely makes sense (I'm assuming you're referring to the section with the grey knob)? The question is whether the solution is to adjust/clean that PRV, or whether it needs replacing.

 

[Spectric]

If you use an OSO cylinder then the pressure regulator is built in along with the safety valves for over pressure / temperature and also the expansion vessels sit under the top cover and all pipe work is on one side so a very clean looking cylinder.

when compared to something like this that uses an internal diapragm for expansion.

 

[Sideways]

The OSO look very tidy indeed and they have a well placed immersion for maximising use of surplus solar energy. Sadly, for an installation under stairs they are not ideal due to proportions and access. My own install avoids pipework at the back of the tank or above it where it's inacessible, works around the tallest / biggest tank that fits the space, and is built so that splitting a few compression joints allows sections to be removed and the whole tank will slide forwards and out for replacement.
If it lasts as long as the old copper cylinder it replaces, I won't begrudge the hours I spent scouring tank brochures to find the set of dimensions and features I wanted

 

[Jake]

Oh right, so I completely misunderstood what was going on in that section. Probably simplest just to get that PCV replaced as it's still the obvious suspect.

 

[sploo]

So here's an interesting thing; I just checked the pressure of the expansion vessel and it's beyond 4 bar (the max my pressure gauge will read). I'd noticed it'd hit 3.4 bar a few days ago, so something is allowing the pressure to creep up and up.

I am going to get a plumber in to replace the PRV, so maybe... maybe... the whole PRV is faulty (and allowing excess pressure to flow to the main cylinder and expansion vessel).