Worth changing from vented to unvented hot water system?

[Spinball]

Hello folks,
I'm looking for some advice and hopefully you can help, please.
Our house built in 1984 is pretty big with two ensuites and a family bathroom upstairs plus two toilets and an ensuite downstairs.
We have two Worcester Bosche 30CDis installed 2013 in the boiler room. We used to have an indoor swimming pool, but it's been disconnected and a false floor being put over it to convert the room into a gym/music/games room.

The hot water tank/immersion heater is behind a plywood panel in an upstairs bedroom.
There are three huge water tanks in the loft.
All three bathrooms upstairs have pumps for the showers and it takes more than a minute for hot water to run.
The ensuite downstairs is the most used bathroom but there is no hot water because it has a separate immersion heater hot water tank which, being electric only, we decided to not use.

The family has at least three showers a day and maybe three baths per week.
We have just under 4 bar water pressure and the hot water and central heating are controlled by Hive.

We are refitting one of the ensuites and have been presented with the option of changing the house to an unvented system prior to installing a new digital shower (Mira Platinum).

We've been quoted a ballpark price of £3,000 to

• Install a Worcester Bosche hot water tank in the boiler room next to the boilers plus pump to circulate the water upstairs.
• Remove the hot water tank upstairs.
• Remove the cold water tanks in the loft.
• Remove the three shower pumps.
• Connect hot water in to the downstairs ensuite by running a hot water pipe down from the ensuite upstairs immediately above.
• Get the system up and running.

So my question is whether generally having an unvented system is so much better that it's something we should try and get.
And whether £3k for the above work is reasonable.
I like the idea of getting rid of the shower pumps and that huge weight of water in the loft, but it's a hard sell to the Mrs.
Many thanks in anticipation of your replies.

 

[Jay The Plumber]

in a word.. yes.

 

[Leo21]

It will be a better solution, but its wether you can justify 3k for something that works.

 

[chris watkins]

Simply yes, if the house was built today then you would have an unvented hot water system.

However (& there is always a however) they will be altering & converting existing pipework which has for more than 30years been at low pressure & now it will be at a higher pressure so there is a risk of leaks, you could ask them to pressure test it which should ID any problems before it is connected to the mains.

The pressure you have is reasonable good & the new unvented cylinder will reduce that down to 3 but the pressure is not the thing you should be so interested in, it is the flow rate . If you have a couple of fitting on at the same time then you want to make sure there is enough water coming into the property to supply them all.

Has the flow rate been tested &/or do you know the size of the incoming mains ?

3K sounds a fair price for that amount of work.

I would take this opportunity & go for it.

PS you won't be able to box in the new cylinder it needs to be accessible for safety reasons.

 

[Riley]

And finally you must have a gas safe engineer for any boiler change AND a G3 qualified engineer to fit the cylinder. Ensure you check credentials

 

[Spinball]

Thanks for the replies. The plumber did say we'd need to pressure test the system.
I don't know about the flow rate. I guess that will need to be tested also.
Is the location of the new cylinder best in the boiler room, or upstairs where the current hot water tank is?

 

[Alert]

A yes from me also, there will be less maintenance cost on the suggested system.

Also I would fit the unvented cylinder on ground floor, if there is ever a water leak then there will be minimal damage, especially with it all being pressurised

 

[JCSPLUMBING]

I would put it in the airing cupboard where the original hot water cylinder is. Regarding flow rate. I would want 25 litres a minute at the outside tap or washing machine valve. Is he upgrading your mains to 22mm also as a lot of houses are in 15mm from the stopcock. This would increase performance by miles as well as long as your mains before stopcock is at least 25mm bore.

 

[chris watkins]

Thanks for the replies. The plumber did say we'd need to pressure test the system.
I don't know about the flow rate. I guess that will need to be tested also.
Is the location of the new cylinder best in the boiler room, or upstairs where the current hot water tank is?

Test it yourself, time how long it takes to fill a large container of a known quantity. So if you have a 25Litre bucket & it takes 30seconds to fill it with a garden tape full on.

The flow rate would be 25/30 =8.33 L/sec x 60 (sec in a minute) = 50 L/M

The plumbers should have established this as you can have high pressure with a poor flow rate or high flow with low pressure.

I would be looking for a minimum of 30+ L/M for a property with that number of fittings.

 

[Spinball]

I would fit the unvented cylinder on ground floor

I would put it in the airing cupboard

So there is the disadvantage of having more trouble if there is a leak with the cylinder on the first floor. Is there a significant advantage in having the new cylinder on the first floor?

Don't know the current pipework thickness.
Upgrading the mains to the house is not an option as it's over 100m under a tarmac and block paving drive.
From the stopcock is going to be tricky also because assuming the pipework is under the floor, we'd have to dig up the tiled floors of the utility room, kitchen and hallway plus the laminate lounge floor to get anywhere near it.
I will ask though.

 

[Alert]

Having a large unvented cylinder on the ground floor is far safer option than having it higher up, I've seen the excess damage caused with water cascading down the house.

Dont get me wrong it's rare and only a recommendation.

You could be prodantic and put the cylinder in a tray with a wet alarm to alert you on any leak before it could get serious

 

[SimonG]

Put the cylinder wherever you want. As long as its properly supported its no more of a leak risk than anything else using water in the house. Poop happens, that's what you pay your insurances for. If we tried to get rid of most hazards you would still have an outside crapper.

Position cylinder to give shortest draw offs to the main areas of usage. Or a secondary return.

 

[Alert]

Pop it in the attic then

 

[Spinball]

Position cylinder to give shortest draw offs to the main areas of usage. Or a secondary return.

The boiler room is over one end of the house, quite a long way from all the bathrooms. The current hot water tank is kind of central to them all.
We had a leak from it last month. Release valve worked its way lose. Ruined the kitchen ceiling. Good advice to get a tray with an alarm if we do have it upstairs.

 

[Scott_D]

What size cylinder has been quoted?

 

[Spinball]

What size cylinder has been quoted?

Haven't got that far, yet. He's preparing the quote.

 

[Riley]

The boiler room is over one end of the house, quite a long way from all the bathrooms. The current hot water tank is kind of central to them all.
We had a leak from it last month. Release valve worked its way lose. Ruined the kitchen ceiling. Good advice to get a tray with an alarm if we do have it upstairs.

secondary return then.

 

[chris watkins]

secondary return then.

From OP
We've been quoted a ballpark price of £3,000 to
Install a Worcester Bosche hot water tank in the boiler room next to the boilers plus pump to circulate the water upstairs.

I read it that they may have allowed for a secondary ? Spinball you need to wait for the full quote but make sure you understand what you are getting.

 

[chris watkins]

secondary return then.

From OP
We've been quoted a ballpark price of £3,000 to
Install a Worcester Bosche hot water tank in the boiler room next to the boilers plus pump to circulate the water upstairs.

I read it that they may have allowed for a secondary ? Spinball you need to wait for the full quote but make sure you understand what you are getting.

 

[Spinball]

Thanks again for the advice. I will talk to the plumber as I don't understand how the hot water plumbing works.
As a side note, we have a 4kw solar voltaic installation. Can excess power be used to supplement the heating of the water?

 

[paulusgg]

Unvented cylinders can go anywhere convenient as long as you can get the water to and from them, obvious I know. The biggest challenge when replacing centrally placed vented cylinders with unvented is the discharge pipework