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Hope all have had a good festive break.
Our hot water system was installed 2009.
It is:
250l
Operating pressure 3 bar
Expansion valve setting 6 bar
In October 2022 the expansion tank on top of the tank burst - suspect not a bad innings after 13 years of service. It basically split at the top - so guess was the membrane was damaged over time.
Local plumber replaced with an equivalent 18 litre expansion tank. A Center CB aluminium one which is supposed to have a 5 year warranty:
<h1 class="MuiTypography-root MuiTypography-body1 jss76 wuk-cached-css-1o2qcki" style="box-sizing: inherit; margin: 0px; font-family: Wolseley-Sans, Arial; font-weight: 400; font-size: 2rem; line-height: 2.813rem; color: #3b3b3b; letter-spacing: 0.005em; background-color: #f4f4f4;" data-testid="product-name">Center CB Potable 24944 potable expansion vessel 18 Litre</h1>
Product code: 597806
Manufacturer code: 24944
However, today this slightly older than 2 years expansion tank has a pin-hole leak on the base
I've shut the water supply into the tank and we still have cold water into the kitchen sink - so can play with things to get toilets working, etc.
Luckily, our nearest Wolseley plumbing supplier has the same expansion tank in stock and I can collect tomorrow morning. I've also left a message, text and whatsapp with the local plumber (lives just along the road) who installed this most recent expansion tank plus a few others who guide they do emergency work just in case.
However, wondered if we have just been unlucky in terms of life expectancy of the expansion tank?
It's also a bit tight to get old out and new in, therefore I wondered if there would be any issues installing a slightly smaller 12 litre expansion tank?
Thanks in advance.
Do not install a smaller expansion vessel.
I assume the vessel you have is white in colour?
The one installed is silver in colour but the original one was white.
The original was a Zilmet branded one.
That looks suitable for potable water so will be fine.
At 18l your vessels already undersized for 250l tank.
CB centre were wolselys own brand..... Bit like buying some no nonsense stuff from Screwfix
You buy it if it's not pressure retaining or with moving parts but you don't use it for critical components.
Thanks T_R.
That's a bit of a concern as the original unvented hot water system was installed by a reputable plumber (2009) was an 18l Zilmet one hence this replacement matched the original install when another plumber had to replace.
What about Flomasta as an alternative?
Thanks!
That’s a bit of a concern as the original unvented hot water system was installed by a reputable plumber (2009) was an 18l Zilmet one hence this replacement matched the original install when another plumber had to replace.
Probably, like the bulk of plumbers, he just fitted what he has always fitted, or what the Wholesalers keep in stock, so that’s why you have an 18 litre vessel. It should be 25 litres or so, I’ve not got my books here to verify, but a quick look online says 25 litres.
Plumbers are taught all the calculations at College, there is even a ‘Design Guide’ book with tables in there, so there’s no need to calculate it, but, they never look it up, and just fit what they think will work.
Sounds like space was tight so an 18l was fitted
It should be a 25l
Will it make much odds . Likely not but absolutely don't go smaller.
Flomasta are bnq own brand.
The merchants in town are open tomorrow. You have city plumbing /wolsley/PTS /plumbase.
Id be phoning round in the morning to see if I could find a new zilmet.
The vessel should have been supplied as part of a package by the cylinder manufacturer. What make of cylinder is it and any numbers from data badge and will be able to find the exact replacement
Cylinder is a Ferroli AQUAcyl/D/250, serial D/250/1040.
A zilmet 24 litre vessel should have been supplied with the unit.
unvented components Europe for spares or advanced water but the first company usually cheaper
Thanks all and Bear for checking. Definitely 18l originally fitted.
I've got both a 24l and 18l on return basis and plumber I trust will be here this morning - as some of the pipes around the tank will need moved to allow removal and fitting.
We'll try to fit the 24l and if need be will cut small hole above into loft space and my mate's joiner son will create a proper trap door type arrangement during the holiday break to allow pressure checking but also easier future replacement of the vessel.
However, wondered if there was an alternative to the expansion tank where excess pressure water could be discharged into drain?
Potentially a thermal expansion relief valve?
Thanks.
However, wondered if there was an alternative to the expansion tank where excess pressure water could be discharged into drain?
Potentially a thermal expansion relief valve?
You need and should in your have both.
The expansion vessels for standard operation. The prv is for release of pressure if the expansion vessel fails
Expansion tanks typical run at around 15psi. If you have truely been running at 6 bar which is nearly 90 psi I’m surprised it lasted a minute.
Expansion tanks are pre charged according to the cylinder it is fitted too, typically 3 bar for unvented cylinders.
central heating expansion vessels generally are set to 1.5 bar.
both are higher than 15psi, you need to be qualified to work on unvented cylinders.
be careful they can be very dangerous should you get a couple of things wrong.
Expansion tanks typical run at around 15psi. If you have truely been running at 6 bar which is nearly 90 psi I’m surprised it lasted a minute.
This is one of the many reasons you don't put a central heating expansion tank on a potable water system
A potable water tank is preset at 3 bar but good for 10.... Well certainly the two I have on my system are. Both zilmet
My grant (zilmet rebrand) central heating one is marked is 3bar max .