Trevi shower stopped working

I recently had a new gas boiler fitted on my open vented system. there was a slight modification to the outside of the heating loop through the DHW cylinder but the DHW supply plumbing was untouched and the flow rate through all the hot taps is unchanged.

My Trevi Boost shower has stopped working though, after being fine for

3 years. I've flushed and cleaned it out but it's still running stone cold at all settings.

I've now noticed that the pressure of the cold supply is reversing the lower pressure hot supply and sending cold water back along the hot pipe.

I see from the installation instructions that there should be non- return valves on each supply pipe. There isn't currently.

Of the 4 recommended check valves in the Trevi installation guide, non were available via Web searches. The only references to them were in on-line versions of the Trevi Boost installation guide.

Thinking about alternative valve sources, I couldn't help wondering how, with both incoming water pressures being quite consistent, why wouldn't the same pressure conditions that forced cold water down the hot pipe when there is no check valve, not just stop the hot water from entering the mixer when there is a check valve?

Dick Treen

Reply to
treenoakio
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I've an open vented system with a trevi boost. I fitted a check valve in the cold side and didn't fit one hot side (as it would restrict flow and cause an extra pressure drop).

My trevi is probably about the same age as yours, and occasionally it will remain running stone cold too - but so far I've always been able to remedy it by twisting the temperature knob from min to max a few times (I suspect it's a bit of limescale forming).

The fact that you're getting cold flow back through the hot supply to the trevi doesn't sound good. AIUI they have a venturi inside that

*should* ensure the high pressure cold flow creates a vacuum to increase the hot flow (see
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perhaps when you cleaned it out something was damaged or incorrectly fitted?
Reply to
RubberBiker

This is what put me off using a check valve on the hot side during the original installation. I've since seen that there are "swing" valves available, with less resistance but they have very different shapes and fittings than the usual plumbing, though I'm pretty sure they could be adapted.

I've now received another message from Trevi. I'm told that because I have 22mm pipework from the rising main to the cold port of the shower unit, it's a fluke that the shower ever worked at all. The message describes it as "imperative" that the cold pipework size be 15mm. the cold inlet port on the shower unit is 22mm though and it's recommended that the check valve on the cold side be 22mm.

As most of the cold water pipework in the house is 22mm from the rising main onward, how much of the length of the pipework branch leading to the bath tap and shower would need to be reduced to 15mm? Would a metre or so have the required effect?

My Temperature knob has had plenty of twisting recently. I also live in a low lime area. There was a lot of whiteish scum on the filter gauzes before I toothbrushed them.

You're right, it doesn't sound good and I was never aware of it happening before. Although according to Trevi, this is a common feature of "Unbalanced" systems and why they advise the fitting of the check valves.

must have been working on it's good days.

This is possible, though I only brushed the filter gauzes on the mixer cartridge and it's now not-working any differently since the clean up than it was not working immediately before.

Dick Treen

Reply to
treenoakio

The message from " snipped-for-privacy@googlemail.com" contains these words:

Are you sure about the incoming pressure being consistent?

ISTR that the Trevi Boost has a requirement for a 3 bar limit otherwise the conditions you describe are likely to occur. Unfortunately I can't remember too much about the shower I installed for my sister a few years ago and, at 250 miles distant, it is a bit too far to go and look at the set-up.

Reply to
Roger

Not exactly but they seem not to vary much visually. I haven't measured them by the recommended methods since just before I fitted the shower. I also didn't keep my notes on those original measurements, although I probably wouldn't have gone ahead if these flows and pressures were outside the spec. Things may well have changed over time.

Being an amateur, I sometimes have a tendency to do a lot more deconstruction when problems arise than is necessary, or than is good for the health of the job in hand. I'm trying to get as much advice as possible before pulling the unit apart again, though it looks like I'll have to take the cartridges out to measure the pressure and flow.

Dick Treen

Reply to
treenoakio

The message

from " snipped-for-privacy@googlemail.com" contains these words:

You can measure mains pressure at any cold water tap fed from the mains. Just adjust the result for the difference in height. Outside taps threaded for hosepipe connectors are said to be ideal for attaching a pressure gauge.

Incidentally I can't see why using 22mm pipe instead of 15mm in the cold supply would be detrimental. It just means that there would be a lower pressure drop in the pipe during operation. I would have thought it might be a problem if you used 15mm when 22mm was specified, too great a pressure drop might restrict the flow too much but given sufficient capacity surely it is the valve that controls the flow, not the supply pipe diameter. Perhaps Trevi could explain their reasoning.

Reply to
Roger

I'm writing to Trevi (Ideal Standard) on quite a regular basis lately and the things I'm learning here are a big help in that respect.

Thanks, that's very helpful. I do have a threaded outside tap and since the bathroom and kitchen upgrades, the current indoor taps don't lend themselves as well to the attachment of hoses as the old variety did. Is there an easy method for calculating the height difference?

Then again, I've just found a "DUALUX FLUSHING NIPPLE BUILT-IN" which came with the original shower kit. It seems like it's meant to temporarily replace the cold (or hot) inlet cartridges for flushing purposes. Perhaps if this could be adapted to measuring the pressure at the shower unit itself, the results would be more directly applicable.

Yes that's what I've been struggling to understand, especially as the shower has previously been working fine for years. But, so as not to rock the boat, I've only so far asked "what is the minimum length run of 15mm pipwork that needs to be introduced into the existing 22mm supply in order to comply with the Installation spec". I've yet to receive a reply on that one.

I've been able to vary the pressure and flow of the cold supply over a wide range by partially closing the rising main stop-c*ck. It seems to me that 22mm pipework offers access to a much wider range of user applied variations than the 15mm pipes would, including those that would be available if 15mm pipework was installed. There may be other limiting factors I'm not aware of.

Dick Treen

Reply to
treenoakio

The "there must be 15mm pipework for cold" argument sounds like BS to me. IIRC the installation instructions made much of the fact that hot supply must be 22mm right the way through - absolutely true and reasonable as it greatly increases low pressure flow. But this statement about the diameter of the cold pipe sounds like some utter numpty at trevi (mis)reading a leaflet and thinking he's an expert.

For pressure measurement, screwfix do a cheap gauge that will fit washing machine taps, and/or outdoor tap fittings:

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Reply to
RubberBiker

On 24 Feb, 14:41, RubberBiker wrote: Yes indeeed!

As I'm still in ongoing communication with the helpful people at the Ideal Standard, Trevi section on this problem I'll need to avoid utter numpty conclusions for now.

I did receive an answer a little while ago to my question about the minimum 15mm pipe run required and was told:

--------------------------------------- "Unfortunately we do not specify a minimum length for the 15mm run as we specify the entire run must be 15mm with no exceptions. We cannot support or guarantee normal operation of the valve outside of these installation requirements."

----------------------------------------

So if the rising main emerged in the bathroom itself, from there 2 Metres of 15mm pipe would conform to the installation spec. But as the rising main is 20 Metres away from the shower, the 15mm pipe run has to be 20Metres long to conform?

The message also added:

------------------------------------------ "If the cold header tank were at the maximum 3.0 metres head, the stored hot water temperature were up around the maximum 75 degs celsius, and the cold mains pressure at the minimum 1.5 bar, this will give the hot water the best chance of getting through if the cold supply pipework was too large."

------------------------------------------

It'll take me a bit longer to pick the bones out of the second part of the message. .

Halfords but the situation is perhaps getting a little too demanding for such bodges at this stage,

Dick Treen

Reply to
treenoakio

The message

from " snipped-for-privacy@googlemail.com" contains these words:

A tape measure held vertically. :-)

I presume you mean converting the height into bar. If so 1 bar is close to 10 metres water head.

Reply to
Roger

Find out what the maximum cold "flow" and pressure is. If flow way too high then insert a flow regulator in the cold line. Available from BES.

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If pressure is way too high fit a pressure reducer too.

Reply to
Doctor Drivel

I can do that. :-)

Yes. That's something I can do too. Thanks a lot.

Dick Treen

Reply to
treenoakio

On Tue, 24 Feb 2009 07:08:55 -0800 (PST) someone who may be " snipped-for-privacy@googlemail.com" wrote this:-

If the cold pressure is outside the specification then a suitable pressure regulating valve in the cold would be more useful than a length of 15mm pipe. However as you have already tried turning down the main stop tap this may not be the problem.

Have you checked that water does come out of the hot pipe at the shower and it has not been blocked by some debris? Is there debris in the hot filter in the shower? Something might have been dislodged or drawn in while the work was being done.

Reply to
David Hansen

...

It does seem that way to me, though any tips from experience are useful and appreciated. I'm working on the basis that there can't be much stopping the shower working as there has been so little that's changed since it was. There are 3 main components in the shower body and I've just replaced

2 of them. The remaining valve is 145quid+ to replace, so I'm trying to ensure that all the less expensive changes are made first. I wouldn't want to spend big bucks only to find it still hasn't done the trick.

I'm not certain about that but it does seem unlikely to be a problem with the cold supply. Unless I can locate the problem and remove it, I'll be working my way through the installation spec again and scrupulously ensuring that the details are followed. I' don't think I'll be prepared to entirely remove the 22mm cold supply and replace it with 15mm though. So a pressure regulating valve may well be next on the list

The flow of hot water doesn't appear to be significantly reduced but it may be affected enough to cause the shower to fail. I'm wondering if a mains pressure hose connected to one hot tap at a time might blow any obstructions back into the header tank where they could be strained out. I'm guessing that any debris wouldn't make it back further than the DHW cylinder though, from where it could eventually be carried back to the problem area.

I've spent quite some time cleaning the filters but the way it's going I'll soon be spending some more.

Dick Treen

Reply to
treenoakio

BES.http://www.bes.co.uk If pressure is way too high fit a pressure reducer

Thanks, I'll be happy to fit either or both of these. The installation guide describes the cold supply in terms of "flow pressure", the acceptable range being 1.5 -to- 3 bar.

One of several things confusing me at present are the charts which show that at 1.5 -to- 2 bar, the hot water temp requirement is 65C min, when at zero head. Whereas, at 2 -to- 3 bar the hot water temp requirement is 60C min, when at zero head.

My practical take on the situation has been that an excess of cold supply was overwhelming the effect of the hot supply which makes the above info a bit counter-intuitive. I've looked at the previous discussions on the flow/pressure equations and it made my head hurt.

Can anyone please tell me: if the cold supply pipes should be 15mm, but instead are 22mm, which in terms of flow or pressure is the one most likely to be in excess of spec?

Dick Treen

Reply to
treenoakio

Find out what the pressure is first.

Reply to
Doctor Drivel

--

Hi again, it's 2.5 bar at the unit itself, well above the min 1.5 bar. Also, the hot water at 65C is flowing at 17LPM through the unit, which is optimum according to the book. I put a swing type check valve into the hot supply pipework to minimise resistance and now the shower works marginally well (lowest combined flow rate through the mixer gets a reasonably hot shower).

On the 22mm cold supply side I notice that only the flow rate changes if I adjust the stop-c*ck, the pressure remains the same. Other than swapping the 22mm pipes for 15mm, the only other option seems to be to but in flow/pressure regulation but as I can change the flow at the stop-c*ck and the current 2.5 bar pressure is under the 3 bar max, I'm not sure if these moves would produce much effect.

Regards, Dick Treen

Reply to
treenoakio

The message from " snipped-for-privacy@googlemail.com" contains these words:

You addressed your question to Dribble but he is mute so far. Hopefully he has finally been sectioned under the mental health act but if not no doubt he will be along eventually to accuse all and sundry (and me in particular) of being plantpots and to confuse the issue with his lack of understanding of basic physics.

If you restrict the stop c*ck enough you will get a measurable reduction in pressure along with your reduced flow rate. I don't know enough about fluid dynamics to know how well that will mimic the pressure/flow rate pattern of a length of 15mm pipe but it is likely that there will be no greater variation between a stop tap restriction and a short length of

15mm pipe than there is between a short length of pipe and a long length of pipe which puts Trevi's need for a 15mm supply pipe into question.

My memory being what it is these days I can't recall the detail of what went before but have you considered raising the temperature of the hot water to change the balance between hot and cold?

Reply to
Roger

I do think this15mm requirement is a bit suspect, maybe just thrown in to allow the Ideal Standard customer services to wash their hands of the problem.

Reply to
treenoakio

Didn't manage to finish my last reply.

Thanks very much Roger. The new boiler has a max DHW temp of 65C, which it's at now, I could get the electric immersion heater set up on a timer to provide

70C at certain times of day. This seems like one of the few remaining solutions.

Regards, Dick Treen

Reply to
treenoakio

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