How to Install a Pressurised Hot Water Tank 

🛠Charlie DIYte Amazon Tool Store amzn.to/3fcLnY4 - all my tried, tested and much loved DIY tools. ☕ Help support me on Patreon -www.patreon.com/charlieDIYte (includes Discord access). 🛍️ Join me on WeShop and earn shares every time you buy! - app.we.shop/join-charliewhite

Excellent video, something I did just before lock down. The hot water tank in the attic had caused a top down flood. That was the cause of the remodelling of the house. I decided to remove the airing cupboard and expand the bathroom. I decided to get someone in to do all the work like you did. That and the plaster are the only trades I have had in. It was something I thought I could do, but living out in the sticks every time I was missing a part would take time to collect. That was great finding out about the relief valve, as I have a clunk whenever I turn on the hot in the kitchen sink. I went to check and I have one, so will bleed it and see what happens. I also watch plumber parts and have been looking at the telsar heater element. I have been thinking of installing it higher up, as I don't need the full tank to be heated.

Had an unvented system for 10 years, love it!

When you see an install like this it takes all the guess work out of hiring a professional plumber. Very nice install even in such a tight space.Thanks for posting Charlie 👏

Hi Charlie. Timely video as I'm having a complete new CH & unvented DHW system installed in two weeks time to replace an old 1970s gravity fed vented primatic system with a Baxi back boiler. I'm currently strenghtening the binders/joists in the attic (yes, in *this* weather) to provide a platform for the tank! From my research there's a few things I can add: - According to the Gledhill installation manual, an unvented system can work off a 15mm cold supply, provided the pressure and flow rates are adequate and you are only supplying one bathroom, which is just as well as that's what I have - The system *must* be serviced at regular intervals, not only to maintain optimum performance and satisfy the warranty, but primarily for safety to ensure it doesn't turn into a WWII sized bomb - There is a specific drain down procedure to follow to ensure you don't pull a vacuum in the tank and damage it. I plan to print it out, laminate it and hang it up near the tank for future use. Keep up the good work!

Very good video. I can't believe how complicated the pipework is.

Great Upload Charlie, you can always check the Expansion tank simply by tapping same with a screwdriver handle, the bottom of the expansion come back with a dull sound, but the Air bladder side of the Vessel gives a higher pitched Metallic Ring to same ...some folk go with the Nuclear option sticking a match into the button on the Schrader Valve to see if water comes out, denoting a burst balloon, but if you loose too much air you would need to pump up the Air Pressure when the system is Cold...

This is a really good video. I have been considering this myself and great to see a video covering the specialist install as well as parts you can do as a DIYer to prepare for the install. I think your content is excellent and always make time for it, including the more specialised topics you have covered.

Always a pleasure watching your videos well and truly explained yo every tiny detail. Much appreciated x

Thanks so much Charlie….so glad you got sorted. We seriously need to get a shower by our house but its rented so we need to get permission first from the Landlord. Both me and hubby battle to get out of our mini bath…..the joys of old age aches and pains….do take care please….much love from South Africa

The Tesla T-Smart is a great piece of kit…. So easy to install and provides real control flexibility - especially if like me you are off the gas grid and rely solely on electric

I’m about to start a whole new refurb on a house so thanks for this. Cheers

I don't know how you do it Charlie, but every time I consider starting a new project, you do a video on it. Bravo and kudos for successfully completing another project!

Great video Charlie, many thanks.

Wicked job Chirag.❤. You did well there with your new recip.

Wise choice getting the experts in😉. Great video as always.

Hi Charlie, I made the decision to go the same way with unvented and Tesla a year ago and haven’t looked back. One really helpful part of the video was explaining all the pipes and devices installed because now I understand how our install actual works! I have yet to box in our install and want to do that now and your cupboard looks like exactly what I want to do, could you do a video to show how you constructed that ? I’m stuck on how the wood fixed to the wall / face frame and door interact

Great video as always! I used the Tesla smart immersion heater in my electric-only flat with a vented system about a year ago. I enjoyed the tech and having the opportunity to be 'smarter' with my hot water temperature, however, I found the cost saving was minimal vs the price of the kit, and not long after I installed it, unfortunately, it stopped working and I decided to go back to the basic immersion heater element. It's definitely a good idea to install it in the higher location as I had mine installed in the lower input and when even a small amount of new cold water came in through the bottom of the tank it obviously showed the water tank temperature was low when actually the 'ready to go' hot water at the top of the tank was hot. I hope you find it more useful than me with your set up!

I researched my options to oblivion on this subject. I went for: Vented thermal store, all DIY install, no yearly plumber inspection, less parts to fail and mains pressure hot and cold throughout the house. The thermal store has two immersions attached to an iBoost box that diverts all extra solar into the hot water rather than going to the grid. The thermal store is attached to the multi-fuel stove as well, so we get solar hot water in the summer and stove hot water in the winter with mains power override if needed (never been needed). The best part about the whole thing - it actually works as intented. Amazing!! Great video as always Charlie, look forward to an update in a year or so.

Very Good Job. Well done Charlie 👍

Hi charlie another way of seeing if the vessel fails is to tap it ! If you get a nice ring tone it's good if you get a solid sonnd it would mean that either the air charge has gone or the diaphragm has failed, it needs checking once a year, to do that valve it off drain the vessel then check with a car tyre gauge if you need to change it use a foot pump or a bicycle pump. I'll also point out that they may come pre charged but not always the pressure you need always charge to the cold fill pressure, hope you find this useful, also love your video's

How interesting, about to have this work done in the next few days. Almost exactly the same setup - gravity fed system + Stuart&turner pump. Cylinder will be in the loft and will (hopefully) have an extra coil for solar thermal in addition to immersion element(s). After having solar PV fitted, I intend to use an Eddi to dump extra power into the cylinder.

Lots to consider, thank you

Thanks for the video =)

Hi Charlie thanks for posting glad the installer pointed out you need an unvented license (G3) to install one. I have done my G3, 4 times now and due for renewal which is every 5 years. I used to tun the T+P pipe (D2) down the outside wall. However this is not necessary. The pipe can be hooked back towards the wall, so long has the outlet distance is, at least the length of the pipe diameter. Nothing wrong here, just less cost and time!

I have installed an Economy 7 tank which had the coil right at the very bottom to maximise the solar divert from a Myenergi Eddi device. I then fitted a cheap temp probe with display in the insulation at the same position as the tank/boiler thermostat to verify the temp of the water. With a bit of trial and error, I set the emersion max temp to just above the boiler sensor temp so that the oil boiler never calls for heat at the scheduled time if solar is available (or has been available). This also acts as a fallback if for any reason the solar hasn't been sufficient to hit the desired temperature in the day. Works a treat and saves a fortune in oil. I also connected the second Eddi output to the electric towel rail so once the water is heated, it kicks-over to warming the towel rail and drying towels when the central heating isn't on. Once that's all sorted water for the day, it switches over to the Zappi which charges the car.... Happy (sunny) days!

Great video. Thinking about updating ours during this year. Is there an increased risk of leaks adding these to an older pipe network? We have a new’ish boiler but the majority of plumbing around the house was kept. Pressure is terrible so really hoping this will be the answer.

Great video!

Always worth having a wet vacuum at the ready for jobs like that where you cut the pipe to instantly suck up any residual water. Seem to remember you have a Titan wet vac, lesson learned for next time and thankfully no damage. Interesting video as ever 👍

You can't use the T-Smart to divert surplus solar though. Either directly or via a PV diverter externally to it (such as iBoost/Eddi/Immersun - others available). However you can use a surplus PV diverter with the "dumb" element below it.

Have the same conundrum, think I’ll do the prep work too. Freeing up loft space as I have a huge horizontal plastic tank

Indeed, I also was looking at such an upgrade but another factor is the annual service typically required by the cylinder manufacturer for the extended often 25 year warranty. Those pressure relief valves have to be tested for correct operation. Even basic immersion heater elements need a double thermostat now for added protection in case the normal stat fails. I think the Tesla immersion heater would be better in the lower flange to heat a greater volume of water.

As an additional point check out priority domestic hot water (heat geek, urban plumber) and see if you can run how water at 70 from the boiler but central heating at 55, in this way your boiler will cycle less and will condense more saving you energy. We have just had new boiler, moved from vented to unvented but also ensured we could do PDHW - also meant we needed a boiler less than 50% the capacity of the old one !

We have had a pressurised system since arriving in Oz 30+ years ago. It’s all there is here

We had pressurised system installed 10years ago, we are on our 3rd preasure vessel, pressure release valve has also gone, tap on the filling sprang a leak, and the tank drain off valve also leaked as washer in it perished. When the mains water preasure dropped and intermitantly cut out a few weeks ago we were totally "stuffed" as no water going into tank meant no water could come out despite tank full. Even hubby says would go back to conventional system as the only problem we had with that after 20years was the cold tank in loft splitting and dumping it's contents through the ceiling - mind you it was a round one which we have since learnt are prone to that. Oh and hubby deals with plumbers every day as he works for one of the merchants.

Hi Charlie, Thanks for the video. Having recently moved into a new home we now have the same issue in terms of hot water capacity due to a smaller tank. Can i ask what the cost of the installation was please. I understand it will vary dependant on installer but more for a guide? Thank you.

Hi Charlie, Great video! We're going to get a new indirect unvented tank to assist with the new shower and bathroom being re-fitted. We have a combi at the moment servicing the rather large 4 bed house. Will it be worth the investment given that 1 shower is electric moving to thermostatic, and the current main bathroom shower is thermostatic also being replaceed with a new thermostatic shower. Essentially i want to run both showers and a tap or 2 and not notice a drop in flow or pressure. I assume we hve good mains as had a new blue pipe put in a few years ago replacing the old lead one.. Any advice? TIA!

Hello Charlie, well what a timely video this is. So i had a new boiler fitted in 1991 (and it's still going) and other than the gas connection i did all the plumbing myself, basically because we were skint. And i was lucky enough to have previous knowledge and someone to check things for me as i went along. So with a header tank in our new 2nd floor , i moved the cylinder to very near, but above the boiler. And wired it as Y plan. But im thinking about modernising the system and dare i say it with some smart features. Thank you for the vids you do i slways get practical advice from you. Please ignore any negativity from others.

Thanks for sharing your experience 🙏 - Water increasing 1600 times in what? Pressure? Volume? Are you sure that is correct?

hi Charlie why didn't keep the shower pump and did you have to keep the same boiler loved the video happy Sunday.

I could be wrong but I think the bore size of the pipework to the shower has an effect on the litres per minute you get at the shower head. If that hasn't changed then the end result would more or less be the same. If the bore size were bigger you'd end up having a more powerful shower but using more water which you may not want. Just theorising.

What are your plans with the old water tank in the loft? Would love to see how you get it out. We are facing a similar challenge and your video came at a perfect time. Thanks a lot!

Hi Charlie, great video as always. How much was the install? I’ve just been quoted £7k! One bath, one mixer shower.

Had you considered a sunamp heat battery?

Hi Charlie I having a problem with low pressure in a 1 bedroom flat would this system fix the problem ?

Thanks, interesting, Does look very complicated and so inevitably less reliable though. Also, not sure I would like to do away with the cold water storage tank these days, as if the water supply is cut it gives a buffer, allowing the shower to still be used.

Please make a video when in case a rad need to be moved and system need to be empty or any other reason who to empty and refil system using this setup?

The immersion will only heat the volume of water above it so where it is in the top slot will heat less hot water overall but heat it up quicker. Given you're running it on solar I'd say use the lower slot as it will heat up more of the tank on the free electric and given it will be running all the time, you don't need it to heat up especially quickly.

I enjoy watching all of your videos, but I am not sure why you allowed so much live electrics to be situated underneath so much water pipework?

Like you say in the vid, these things are not a DIY. You need HWSS to fit vented cylinders too, they just don't need a cert. Unvented is just the G3 part of HWSS. The hardest bit of retro fitting venteted to unvented is finding a path for the discharge and maybe uprating the mains. If you dont like the look of the discharge pipe Charlie. You can shepards hook it towards the wall where it comes out the wall in most cases. The fancy pants immersion would be best lower down. The dumb one above for back up/boost. If you find yourself running out of hot water. Its best to up the temp. Effectivly gives you more hot water when it's mixed down at the taps. Think of the hotter the water the stronger the squash in the bottle. You need less squash to make a glass. You can get flash with unvented with near instant hot water at the tap if you do a hot water return. It saves time, water and energy. That mythbusters vid is one of my favs. If there mockup had walls as well. They would have been blown out too.

Great video, one quick question. With energy prices going up what’s the difference in running costs between the two systems?

looks good BUT YOU have a leave ball ( i know handles off but that needs removing) valve on that expansion and that a NO NO should hard pipe with no means of isolation

Hi Charlie you can get a discharge bucket for the prv that prevents all the effort of ripping up your floor and having the pipe work running down your outside wall.

Can I have your views on floor heating ? Electric or pipes please help

As an additional note the hot water coil in the new tank is probably much larger than the old one, maybe as much as 15kw now v 3kw in the old one so your hot water recovery time will be much better.

Charlie does this mean you no longer have header tanks in the loft for water and central heating. I am looking at a loft conversion for a bungalow and to create a plant room so this sounds an ideal system to work with my oil boiler. Great video and very informative. Does your plumber work in the Stafford area?

Thanks for the video. How much did you pay for this job?

I don't have a quarter of the DIY skills you have but I wonder if you should have had some plumbers mate on hand when cutting that tank pipe, would have allowed you to block the opening while you got your towels to hand. Hope the cut heals well. x

I got,that Tesla. Maybe because of you, I can’t remember. But it’s great fit and forget. Till you need it. Then it’s there. Brilliant.

Hi Charlie, great video as ever. Just wondering if you have any concerns over the reliability of the T-Smart thermostat? I see it has lots of negative reviews from people saying it only lasts about 6 months.

Always worth having a wet vac on hand, and turned on, when cutting into pipe work I think

Hi Charlie. Very interesting video and this may not be the place to ask for advice but I'm wanting to install a 7kw solar system with 10kw batteries and I want to go completely electric. Ie radiators and hot water...could you spare any advice....thankyou

Just watched your vid, which on the whole was very informative, however there is a point of concern regarding your install. there should be a minimum of 300mm unobstructed vertical drop from your safety valve to the tundish, I don't think this is achieved looking at your pipework. (the 15mm elbow) In addition to this, you should never fit an isolating valve to the pipe going to the expansion vessel. I know the handle has been removed to prevent isolation during use, but there is always that one occasion when some inexperienced person will inadvertently isolate that supply and then you're in trouble.

Will be getting one of these myself, but to replace an old unvented cylinder which is rusting away. Problem is, the newer tanks hold a lot less water than the new ones but occupy the same space, i think it’s down to them using more insulation. So having to go down from a 210 litre to 180 litre tank. I might have to put an extra heat cycle through it, or warm it up more.

If we're looking to divert surplus solar PV to your hot water tank it would have been better to fit a solar immersion controller such as the iBoost or Eddi with CT clamp so you really only do divert surplus

George Wet n Dry vacuum should always be on stand-by when plumbing. Draining tanks, radiators and pipework with a vacuum ready for unplanned wet experiences. Dropping a radiator- don't put a bucket or tray under. Start the vacuum and let it suck up every drop. If draining pipework, use vacuum to suck pipes dry opening an air inlet at the opposite side. This way - dismantling dry pipes with almost no residue.

In 1982 there was a horrific accident in the USA when 7 children where killed as a result of an unvented cylinder exploding. It vital the safety system is fully operational, as states in the video

Hi Charlie I am confused as you said at the beginning that you put in a pressure pump to increase the water going to the shower and then almost immediately say the you had nine bar of pressor from the road? I myself have an on demand heater and have never had any issues from that day on

is pressurised hot water tank keep the water hot for longer?

Great video, as usual, and whilst this is youtube (with appropriate affiliate links etc to yourself) / entertainment - it nevertheless doesn't make any financial sense to receive a bit of extra hot water in the kitchen (£3-5K??? to add i bit of heat from your panels? - even at 3p pKWhr SEG for excess power will never cover your initial outlay in your lifetime with this retrofitting system) - for a perfectly working system (yes if it was at the end of its working life, maybe??) - you would be better off adding extra insulation (to the new 450mm in your loft).

I have never put an isolation valve on an expansion vessel I have never needed to sounds a bit dangerous if you ask me, if they had put the cold water main in to the bottom of the multibloc valve and positioned it above or at the same hight of the cylinder, and put the expansion vessels above the cylinder you wouldn't have problems working on the expansion vessel or the multibloc valve, all you would need to do is turn the lever vale off before the multibloc or even the mains stop tap where it enters the building and open the hot and cold taps and your good to go, you could even open the pressure reducing valve to dump the last of the water in the vessel, there a sticker on the Gledhill cylinders that tells you to do that

Do you notice much difference in your energy usage using your excess solar to heat your hot water over using your oil boiler?

I just wondered what happens when you finish the house, are you stopping with this channel or are you going to move, cause I really like this hehehehe Okay some comments: 4:50 You look a bit like "Hansje Brinker" a character from our Dutch books (look it up) hehehehe. 10:10 I would definitely take that box of the floor and mount it upwards on a piece of wood/board or so at least a couple inches/cm from the floor. Looks you got it all covered successfully, job well done I may add. Thanks for sharing. Did you have any reply from your insurance company about the solar panels. A friend of my recently added some panels (here in the Netherlands) on his house, called his insurance and it was all okay, they just added the value of the panels and components to the value of the house and it even didn't cost him extra money but now it is covered in case of fire or damage cause they know he has got it. There was no extra cost for fire insurance either cause it could be an extra fire risk.

Are those Munsen clips screwed into the tank?

👍

I'm just reading through Gledhill's installation manual and I can see why the plumber removed the handle from the valve going to the expansion vessel: 'There must be no valve on the pipe work between the expansion cylinders and the unvented cylinder which could prevent the expansion of the water contained in the unvented cylinder reaching the expansion cylinders.' I wonder if a pedantic Building Inspector would fail your installation because of this?

How much heat in degrees does your tank lose in a 12hour period?

I have gravity fed, but flow is really poor so I doubt I can go with a sealed system

I’ve never understood how does a householder tell how much hot water is in the tank? There’s no visual indication?

This has performed exactly as desired ru-vid.comUgkx8G49mV71sAzUl9shXyLW-r3XgHH9EVh1 . Basically, instant hot water instead of waiting up to two minutes as it was before. I have had this installed almost exactly one year now and just replaced the anode which is pictured. I pulled it out at six months and cleaned the heating element and removed debris. I would recommend a cleaning every six months and an anode replacement yearly. A mild citric acid and water solution soak really helps clean the heating element and tank. It must be fully disassembled to do the cleaning and that is not difficult but could have been made easier with a couple of design changes but no big deal.

Good general video but just one comment about the danger of explosion when a hot tap was turned on - in the case of the unvented cylinder going way above 100°C under high pressure if all the safety devices weren't fitted or disabled and the immersion got stuck on. Yes it could go to a very high pressure eventually but opening a hot tap wouldn't cause a steam explosion due to dropping pressure. At most it would be a scalding risk and you'd know something was wrong from the force of scalding water. The pressure in the tank would not increase due to opening the tap, that's nonsense. As the pressure drops, the boiling point reduces creating steam which balances the pressure back to the same point before the tap was opened but no more. It self regulates. If the tap was left open the pressure would slowly drop as the tank drained and cold water came in. That's exactly the same as a pressure relief valve operating. Think about it. If letting hot water out caused an explosion then safety pressure relief valves wouldn't work! Of course if there was no pressure relief valve (or no hot tap opening) then in the event of a thermostat failure (which by law also needs a safety cut out) then pressure would increase to the point of explosion - which it's what MythBusters did. High pressure boilers like steam engines work at very high pressure and temperature and they all work by letting some super heated water out which turns into steam and expands to drive the engine but it doesn't cause an increase in boiler pressure and a boiler explosion. The pressure is maintained until the water runs out. That's why you fit safety cut outs and safely regulate the heat energy applied and the install must be done by someone with the correct training so these devices are not compromised.

Why is there a pipe on the outside?

Isolation valve inline with expansion vessel 🤔 I'd install a notice DO NOT MOVE.

The big win is replacing an electric shower on the incoming main on the top floor of the house that didn’t have enough drop from the header tank with a normal shower (yes you had the pump, we didn’t)

Charlie, what kind of boiler do you have? We got one of these gledhill tanks installed and transformed our combi boiler into a system boiler. What I’ve noticed however is that the water does not stay warm in the tank for long periods of time. I’ll wake up in the middle of the night and the boiler is running to top up the temp (which is set to 45 degrees) Is that normal? Sometimes I get anxiety of gas usage so I switch the boiler off in the night and in the morning, the water temp has decreased. My installer (although qualified) doesn’t really provide a useful answer. I just wish I could get Roger Bisby to come take a look at my set up. 😹

The stuff you find on the internet, I have had all this stuff in my airing cupboard for 16 years and no idea what it all did … For those with a cheap overnight electric EV tariff you can buy fused spurs with timers built in so can fill the tank with hot water on cheap electricity. Ours lasts all day with no problems. 5 minutes to fit.

So the first question I have is… why not use a combi boiler? No tanks necessary

Always loved your videos Charlie, but you’re clearly deviating to the ‘advanced’ end of the DIYer for your videos. Obviously you’re doing well from it and I wish you all the best, but the reason I found your channel so endearing was it encapsulated low/medium DIY skill set. Just be careful that you might lose the casual viewer over time

How to install a tank? Get your mate round who has the correct qualification (hopefully.) actually, not a tank, it's a cylinder.

Twice as many water leaks since both hot and cold water will be at high pressure

This is the Mythbusters cylinder explosion mentioned: ru-vid.com/video/%D0%B2%D0%B8%D0%B4%D0%B5%D0%BE-9bU-I2ZiML0.html

Don't think an isolation valve is allowed between cylinder and expansion vessel, if left closed by mistake or someone closes it that has no knoledge of unvented hot water system you could have a very dangerous situation

Just to confirm, these can explode if you don't have all the safety devices in place. I was in Sardinia and the hot tank in the bathroom between two bedrooms over heated and exploded. It looked like a hand grenade had gone off and destroyed the bathroom. Luckily nobody was in the bedrooms. Don't take a chance , use a qualified plumber.

"This can be really, really dangerous so you need someone qualified to fit it" "It's only a one - day course..." Wow....

I don't agree with the bomb. The water can only heat up to the temperature of the water coming from the boiler. Basic physics

Wouldn’t touch Gledhill. I was unlucky enough to buy a house with one of their Boilermate systems, and they had withdrawn all support for those utterly appalling systems within just a few years of their manufacture. Can’t be trusted.

Remember that to install an unvented cylinder by law you MUST be qualified and trained, they are pressured bombs if anything goes wrong.

Big fat fail, isolation valves on hot no no

"Obviously that's coming from your boiler". And why was that Obvious? Obvious to you only. And the hand that teaches flies all over the pipes so than no one wanting to learn can learn anything. Classic expert error. Not considering what the learning audience needs to learn. Specifically, slow and detailed.

Excellent coverage of the subject Charlie - thank you. Did you not consider taking the vent away from the combination valve and pressure relief to an internal soil stack(Page 3 of this: www.nhbc.co.uk/binaries/content/assets/nhbc/tech-zone/nhbc-standards/tech-guidance/8.1/discharge-pipes-from-unvented-hot-water-storage-systems-.pdf), rather than routing externally, or was that not an option due to local circumstances?