Plumbing issues driving me mad - help needed please

[Plumbingdrivingmemad]

I have been experiencing an issue with my heating system for the last few months and really need suggestions as to what might be going on.

My system comprises an LPG Ideal Boiler and OSO Tank, with wet underfloor heating downstairs, 2 radiators upstairs, and hot water

The Boiler heats the water in the OSO pressurised tank, the water in the underfloor system and the radiators upstairs.

The whole system is 7 years old and has been annually serviced since new. I have a really good plumber who has always undertaken the servicing and I have only once needed to call Ideal out to replace a pressure vessel in the Boiler.

Suddenly three months ago the system developed a whistling noise, which sounded as it was coming from the Tank and a pinking / cracking noise which also appeared to come from the tank.

My plumber visited, carried out the annual service on the Boiler and tank and I assumed that would be that.

The problem continued and got worse. Ideal visited and advised it was definitely not the Boiler. They suspected a Two Port Flow valve.

My plumber changed the Hot Water Two Port Flow valve and upgraded the Auto Bypass valve. Still the problem continues.

I phoned OSO, they had no idea what could be wrong.

Could anyone make any suggestions as to what could be going on?

• The issue is a loud whistling from the system approx. 20 minutes from the point at which the Boiler starts heating the hot water. That continues for 5 minutes and is then accompanied by the cracking / pinking noises, which I believe are coming from the tank.

• The issue also arises when other elements of the system are off and the Boiler is just heating water for the upstairs radiators. In this scenario there is whistling but no cracking / pinking noises from the tank.

• There is no issue when just the underfloor heating is on

• And no issue when heating the Water using just the immersion heater. The tank is totally quiet in that scenario.

My plumber is returning this week to change the Upstairs Heating Two Port Flow Valve and the Thermostat in the OSO cylinder, but this is all getting very expensive and if those upgrades don’t work I am concerned as to how we find what the underlying cause of the issue is.

Has anyone experienced anything similar or have any ideas as to what else might be causing these issues. Any help or advice would be really appreciated !!

I don't have much general knowledge re boiler systems, but I was wondering if it was a thermostat issue.

I would contact the manufacturer of the cylinder directly and describe the experience that you are having. They will almost certainly be able to give you some advice.

Also google your cylinder and whistling and look for similar reports, eg here :

forums.moneysavingexpert.com/discussion/4328417/whistling-ringing-from-hot-water-cylinder

Also, is your plumber G3 ?

@GasPanic

I contacted OSO direct several weeks ago. They said it is not an issue they have come across before and hence have no advice as to what it could be.

Yes my Plumber is G3. He is an excellent plumber and has tried everything he can think of. Hence the changes to the Flow Valves, new Auto-bypass valve & Tank Thermostat.

He is also good at reassuring me that the Tank is not about to burst. I had that experience years ago with a Megaflo tank that caused £££ to clear up. Hence I am very nervous 😱😱

I have googled my issue but not found answers yet. Hence turning to Mumsnet. Although I have name changed recently I have been here for years and know how often someone else will have experienced just this issue and know the cause.

I googled "unvented tank whistling" and got a number of suggestions from google AI.

Whistling I would argue is normally associated with pressure build up. I would argue that the pressure operations of the tank is far more likely to be the source of your problem, so expansion vessel in the tank if it has one or TPRV which someone on line cited as an issue. I would be looking at these rather than changing the flow valves or thermostat. The problem is that it is difficult to get inside the tank to find our what is wrong so in terms of tank operation the TPRV valve change is probably the only easy thing to look at/potentially replace, otherwise it is a tank replacement as it is hard to see inside.

I am not an expert but have spent a considerable amount of time learning about my own unvented system (Megaflo rather than OSO). I had the TPRV replaced on my system a couple of years ago because online suggested 20 years was a fairly long time for these things to be in use without replacement.

Maybe someone will come along with more experience of this and have some comments.

Thank you @GasPanic

I will search online again, but will definitely discuss the TPRV with my plumber tonight.

I think that was ruled out because there is no flow through the Tundish, but I am now not certain what else we have left to change.

I will also be discussing a tank change if this is not resolved tomorrow. The stress of this issue is now becoming far too much.

I guess it could be air coming through the TPRV, although I don't know what scenario would cause that. I would have thought if there is air escape through the TPRV the plumber should be able to localise that.

Bumping here and wondering if @Pigletjohn is also still around to help.

My plumber has been out again and still we cant resolve the issue.

We have now changed the Auto Bypass valve, the Hot Water flow valve, the Upstairs Heating flow valve and the tank thermostat. And still there is whistling 20 minutes or so into the water heating and upstairs heating cycles and the tank starts popping / cracking a few minutes later. That goes on until it stops calling maybe 10-15 minutes further on.

My plumber has spoken to the company who installed the Underfloor Heating and has ordered a new valve that controls the water feed to the manifold in case that is the cause of the whistling. We noticed that it stopped on one occasion when the water was heating and we switched an underfloor zone on, so 🤞🤞that might be one of the issues.

But, and it is a big but, the tank continues to pop / make cracking sounds approx 25 minutes into the cycle, or earlier if the water in it is still very hot. The valves at the top if the tank seem to be working fine and my plumber has checked all the pressure vessels again. The fear is that the tank is overheating / being over pressured but with a new thermostat in place we don't know why.

Ideal came out right at the start of this saga and declared the boiler fine. However we have subsequently noticed that the Boiler temperature gauge is not responding to attempts to turn it up and down to control the boiler temperature. They are booked to come again, but the earliest appointment is another week.

Has anyone experienced a similar issue in the past and could they throw any light on what the issue might be?

This is all becoming eye wateringly expensive, my poor plumber is spending hours trying to identify the problem and my stress levels are off the radar.

Any help would be much appreciated. !!