Gravity shower started airlocking


Postby Probe » Tue Jan 26, 2010 5:51 pm

Hi,

I have a Triton "Thames" exposed shower supplied by a combi boiler.

The shower (and boiler) is about 3 years old and has worked perfectly until recently. The shower is fed from overhead.

In the past few weeks we cannot get anything hotting than luke warm water out of it. If I unscrew the chrome blanking plug on the top of the mixer a small amount of air vents. The shower will then put out nice hot water but only for about 10 seconds at which point it becomes tepid again.

I'm guessing this must be an airlock, but I don't understand why it's suddenly started.

Has anyone any ideas?

Thanks
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Postby plumbbob » Wed Jan 27, 2010 11:32 pm

Confused! You can't have a gravity shower with a combi boiler. Reasons for the problem can be different depending on whether the shower is gravity or mains fed. Which is it?

One possibility though could be a blocked filter (if fitted).
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Postby Probe » Thu Jan 28, 2010 10:04 am

[quote="plumbbob"]Confused! You can't have a gravity shower with a combi boiler. Reasons for the problem can be different depending on whether the shower is gravity or mains fed. Which is it?[/quote]

One thing I'm very competent at is confusing people!

The shower is definately mains fed, I wasn't thinking straight when I posted the description. I'll check for a filter but I'm reasonably sure I didn't see one when I re-located the shower about 9 months ago (before you ask, the shower worked fine after I re-located it!). We do live in a hard water area so I guess limescale could be an issue if a filter is fitted.

I must admit that the s/s feed pipe is definately hot to the touch which maybe also indicates a blockage/restriction in the mixer?

I checked the temperature regulator setting last night and it's still unchanged on the origianal red paint (tamper indicator) markers so, presubably, that can be discounted.

The thought crossed my mind that maybe the mains pressure has increased resulting in increased bias to the cold??? Would this sound possible or should any pressure fluctuation equal out?
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Postby plumbbob » Thu Jan 28, 2010 10:39 pm

Ok, so if we are talking about a pressurised system we can discount airlocks as a cause. Air can't get in anyway, and if some does, the pressure will force it through.

So what does that leave? Well, three possibilities maybe. Firstly, a blockage - a filter has to be favourite. The second option is a failing cartridge. Maybe you should remove the stops and allow the temperature setting to go beyond the maximum. Does that cure it?

A third possibility and probably more likely after your last comment is about the imbalance in hot and cold pressure since the increase in the mains supply.

Some showers cannot handle the smallest difference so if your boiler restricts the hot flow, and some do (Vokera is one), then flow restrictors have to be utilised.

Oh, I have just looked at the installation manual and it shows (Fig 2 page 2) both filters and restrictors fitted in the feeds. I think you need to check these are clear and installed the right way round before venturing any further?
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Postby Probe » Fri Jan 29, 2010 5:01 pm

Thanks Plumbbob

Bizarre that, without any intervention from me, the damn thing is now putting out decent temperature water once more :?

I suppose a blockage may have shifted to allow better flow or the mains pressure has resumed "normal" pressure.

I'm still going to check the filters, though!

Oh, in case it has any bearing on things, the boilder is a Greenstar 24i junior, regularly serviced etc. Most service engineers have praised the make/model as being a good one, despite having to change the control panel twice in consecutive years! (good job I have a service contract!).

Will update with any findings
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Postby Probe » Wed Apr 21, 2010 8:35 am

Just thought I should post that my problem was that I'd used (too much) jointing compound on the olives of the feed pipes and some had partially blocked the s/s filter. Dis-assembly and tedious cleaning of the filter in situ (as I don't had a doodad to unscrew the retaining nut) sorted the problem.

Interestingly, we also had the boiler serviced a week later and we suddenly had a massive increase in water temperature through the shower. Whether this was anything to do with the service (they didn't mention finding anything awry) or whether another blockage suddenly cleared, I don't know, but either was, we're happy now! :D

Thanks to all who replied.
Probe
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