Could I converting to unvented without replumbing?

[DoItRight]

Hello & thanks for taking the time to read & reply:
I'm new to this so apologies if my terminology isn't quite right


My old vented cylinder is about to give up the ghost so I'm wondering if this is the opportunity to swap to an unvented system, so that I can get rid of the tank in the loft and improve the pressure throughout the house.

We have a blue pipe from the mains, and 6 of the 8 pipes throughout the house are 25mm (no idea which are CH and which are tap water) but my luck the two 15mm are the latter
I believe/hope the potterton Promax HE is up to the job (10 years old condensing 15kW heating only boiler)

The main problem, I believe, is that we have an extraordinary number of 90 degree elbows throughout the house (semi) which probably explains why the hot water flows into the bath at about half the rate of the cold water.

So would we actually get the full benefit in switching to mains pressure, or would we also need to "improve" the plumbing?

As a side note I'll also be switching all the rads to TRV's all hooked up to a home automation system.

Thanks for any thoughts / opinions / advice

P.S. There's nothing wrong with the boiler which is why i'm not really considering switching to a Combi (which would face some of the same issues)

 

[Mike Jackson]

Without looking at the job it's not possible to say. This is not a DIY job as you need to be G3 registered to fit an invented so why not get someone in to advise/price.

 

[SimonG]

Static Pressure, Dynamic Pressure, Flow Rate?

As MJ says not a DIY job. G3 registered engineer required. Get yourself at least three estimates and go from there. Or post your location, there may be members of the forum local to you who could assist.

Welcome to the forum 🙂

 

[Whn1]

Sounds to me that your cold water is off the mains which is why it seems much more powerful than the hot. If the were both tank feed they'd be of a similar pressure. You'll always benefit from pressure by installing an unvented as long as your old pipesizing is ok you'll benefit from flow too. You need to make sure you have at least a 22mm water mains to the point where you'll be siting the new cylinder you'll also have to take into consideration the safe discharge of the prv and tprv. Without seeing your property is hard to say if all of the elbows on the pipe you're saying will interfere with the performance but I highly doubt it. For your information the 25mm pipes you talk of are most likely 22mm 😉 hippie this helps.

 

[Whn1]

I must add definitely not a diy job. Fitted incorrectly unvented cylinders can be extremely dangerous.

 

[Ermintrude]

Yes very possible and if it's a modern house with soil pipe boxed in kitchen that passes all way to loft = very possible

 

[Dotty]

Assuming you're talking about the pipework between the HWC and the outlets then yes, you shouldn't necessarily need to get them replaced but I should get it checked if I were you.

As both Mike and Simon have correctly stated this isn't a DIY job, in fact it is a criminal offence under part G3 of the building regs for someone without the relevant qualification (G3/unvented) to install or maintain an unvented HWC.

Get 3 or 4 quotes and don't go for the cheapest!

Good luck!

 

[Dotty]

Sounds to me that your cold water is off the mains which is why it seems much more powerful than the hot. If the were both tank feed they'd be of a similar pressure. You'll always benefit from pressure by installing an unvented as long as your old pipesizing is ok you'll benefit from flow too. You need to make sure you have at least a 22mm water mains to the point where you'll be siting the new cylinder you'll also have to take into consideration the safe discharge of the prv and tprv. Without seeing your property is hard to say if all of the elbows on the pipe you're saying will interfere with the performance but I highly doubt it. For your information the 25mm pipes you talk of are most likely 22mm 😉 hippie this helps.

I must add definitely not a diy job. Fitted incorrectly unvented cylinders can be extremely dangerous.

Bloody hell! It's Amazon Tony!

 

[Whn1]

I'm still alive cropp 😉 was keeping a low profile hoping you'd all forget about that.

 

[SimonG]

I'm still alive cropp 😉 was keeping a low profile hoping you'd all forget about that.

There's two things that will never be forgotten, one was the amazon cheap tools and the other was Zebs slip up 🙂

 

[Irish]

There's two things that will never be forgotten, one was the amazon cheap tools and the other was Zebs slip up 🙂

aww man I know nothing about either of these??????

 

[Dotty]

I'll bang something up in the Arms

Best get this thread back on track.

Mr DoItRight,

Do as your name suggests buddy and do it right by getting a qualified guy in.

 

[Ermintrude]

What Mike the night? That pleb not got Edge let along 3G?

 

[Ermintrude]

http://youtu.be/jPIwUyXhug4

 

[DoItRight]

Thanks for the feedback guys

Just to clarify - I have no intention of DIY, I know my limitations and have read up just enough to know about the law on the subject.

I was just seeking feasibility and better understanding

For instance does the cylinder expansion cistern still have to be in the loft, or could it be directly above the cylinder (or what about the merits/safety of the air bubble type unvented cylinder?) - I guess that's where the PRV and TPRV come into the equations ...

 

[Dotty]

Good man. The proximity of the EV and safety valves depend on the manufacturers instructions of whichever tank your guy gets for you..

And bubble tops can create their own problems. Get your guy to show you how to reset the bubble if you get one.

 

[AWheating]

cylinder position needs to consider the discharge pipework route and the cylinder weight mainly. most other things can be routed to it fairly easy. your system controls will prob need upgrading but must still compy to part G and part L. your boiler will prob be sized ok if your currrent system works well and you warm your hot water at a different time of the day to running your heating system.

most of all get a competent person in to advise you correctly and install the system.

 

[Subby]

Seems like the right time to post the old mythbusters clip
https://www.youtube.com/watch?v=fUkjXGfCLIM&list=UUuvsM1GZB7qp3gbwKjsGzkg
A video showing the importance of having a hot water cylinder installed properly, also serviced and checked, as the effects of a unvented hot water cylinder exploding are devastating!

 

[DoItRight]

With regards to pressure, I should probably have mentioned that both boiler and cylinder are on ground floor, right next to mains

so bathroom cold water flows straight down from loft cistern, whereas hot has to flow all the way down and back up one floor again.

I'm hoping an unpressurised system would equalise those noticeable differences (by HW not having to flow through lots of elbows twice).


Interesting point about running CH and HW at different times. I've always run both together for the implied gas economy (i.e already heating the house, so might as well do the hot water too), but now wondering whether that's really as effective as it seems ???

By system controls, do you mean pumps, filters & valves, or timers & thermostats (which will be replaced with Home Automated equivalent, by a Pro)?


Thanks again for the great feedback from everyone

 

[Sparkgap]

Seems like the right time to post the old mythbusters clip
https://www.youtube.com/watch?v=fUkjXGfCLIM&list=UUuvsM1GZB7qp3gbwKjsGzkg
A video showing the importance of having a hot water cylinder installed properly, also serviced and checked, as the effects of a unvented hot water cylinder exploding are devastating!

Some years ago some yobs torched a chemistry lab at a local school. The main hot water pipes from the boiler room ran through the ceiling above the lab. The water flashed to steam and shot back along the pipes into the 200 gallon cylinder and blew the bottom out (despite there being a 3/4" safety valve on it), causing the cylinder to leap about three feet in the air and smack a 5" gas main above it.
Poor fire brigade turn up to find lab on fire, chemical hazards, flooding and a gas leak! 😱