Gravity fed system for loft conversion - advice please

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Hi all,
Am after some advice.

We currently have a 3 bed, 1 bathroom & 1 ensuite house.

We have a truss roof and want to convert it to make another bedroom plus additional en-suite.

3 companies have quoted so far – all loft conversion specialists.
We have a gravity fed system. Large cold water storage tank currently in loft, with hot water tank in airing cupboard on 1st floor landing.
We would like to retain this gravity system – move the hot water tank into an airing cupboard in the loft and raise the cold water tank into the eaves.

Max height in the loft is 2.3 metres.

All three companies proposed to keep the gravity system and move the hot water tank into an airing cupboard in the loft and raise the cold water tank into the eaves.

We prefer one of the companies over the other two. Mainly because he seems more diligent and trustworthy and comes recommended.
We have had three separate meetings with this one company. The last being recently with the company owner, together with the heating engineer/plumber he uses for most of his loft conversions. His heating engineer/plumber has been and had a good look and thinks there is not enough headroom between the top of the hot water cylinder and bottom of the cold water tank. He believes this would cause pressure problems – especially for the en-suite in the loft.

His recommendation is to either have a combi boiler or megaflow system. Of the two, he thinks a combi would be best. Either system would mean the shower in our bathroom would need to be replaced as it is pumped from the shower unit on the bathroom wall.

I have only had one meeting with the two other companies and they both suggested keeping the existing setup and that it would be ok with the loft conversion.

Pressure and flow rate for mains water I do not think will be an issue.

Am wondering if anyone can provide me with some advice for the above please? I have always been against combi boilers as several places I’ve been to have had combi boilers and opening other taps when having a shower or flushing the toilet causes water pressure to drop and quite often water in shower gets piping hot or suddenly goes cold.

Thanks in advance
 
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Coffin tanks are designed to hold a lot of water and can be installed up high out the way.....google them.
 
i agree with the plumber that came round, i don't think it will work you just haven't got the height even with a coffin tank, you will have three bathrooms so i wouldn't go the combi route, unvented if you have the flow & pressure, why can't you leave the cylinder where it is ?, if you don't go unvented then unless you want an electric shower or go for a neg head pump then a shower in the roof won't work, don't forget even if you can get it high enough which i doubt you still need to be able to get to it & be able to change the ballvalve
 
i agree with the plumber that came round, i don't think it will work you just haven't got the height even with a coffin tank, you will have three bathrooms so i wouldn't go the combi route, unvented if you have the flow & pressure, why can't you leave the cylinder where it is ?, if you don't go unvented then unless you want an electric shower or go for a neg head pump then a shower in the roof won't work, don't forget even if you can get it high enough which i doubt you still need to be able to get to it & be able to change the ballvalve

Many thanks for your reply. It is much appreciated. Assuming I go with megaflo cylinder, which manufacturer would you use and what size cylinder would you recommend?

Dont suppose you would be prepared to provide me with a quote to supply and install? Am in newbury, berkshire

All three loft companies proposed to use the existing airing cupboard space as new stairs access point for the new loft conversion. Hence the need to move up into loft.
 
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Just remember that any sealed system (megaflow type) needs to be installed by a plumber who is qualified in unvented systems, make sure you check his credentials, he spent time and effort and money getting them and will be pleased to show them to you. By the way Megaflow is one of the makes rather like Biro and ball point pen, Megaflow is an unvented hot water cylinder.
 
You'd be surprised at how many times, when asked for a ballofix and I asked "Do you want a real Ballofix?" the numpty on t'other end of the phone replied "Eh?" :rolleyes:

Generic terms, don't you just love 'em.
 
A worcester highflow 440/550 boiler or similar would give good DHW flow rates for 20 mins, and relieve you of all the tanks - worth a look.
 
I normally use Ariston, megaflows are too expensive & as they contain the expansion within the cylinder you lose a certain amount of h/w storage, size depends on your currant & future h/w requirements
 
I normally use Ariston, megaflows are too expensive & as they contain the expansion within the cylinder you lose a certain amount of h/w storage, size depends on your currant & future h/w requirements

How do you work that out? Surely a 300 litre megaflo holds 300 litres, with a bit of expansion spce on top of that. :confused:
 
A worcester highflow 440/550 boiler or similar would give good DHW flow rates for 20 mins

how do you work that out ?

at the req pressure either 1.5 bar or 1.7 bar will give you 20-25 ltrs/min then reverting to combi mode @ about 12-16 ltrs/min so given that the storage is 51 ltrs you be back to combi mode in 2-2 1/2 mins

The Greenstar Highflow CDi combi boilers are floor-standing. These boilers have been specifically developed for larger two bathroom properties where there is a heavier requirement for heating and hot water.

440 Domestic hot water flow rate: 20 litres per minute at 30 degree temperature rise (provided adequate mains pressure is available)

550 Domestic hot water flow rate: 25 litres per minute at 30 degree temperature rise (provided adequate mains pressure is available)

way to go WB to make your product seem better than it is, the world & his wife work on a 35 degree rise, plus have you seen the price of these things
 
I normally use Ariston, megaflows are too expensive & as they contain the expansion within the cylinder you lose a certain amount of h/w storage, size depends on your currant & future h/w requirements

How do you work that out? Surely a 300 litre megaflo holds 300 litres, with a bit of expansion spce on top of that. :confused:

sorry i didn't mean it as it sounded :oops:
what i meant to say was for the same given pysical size
 
The highflow are a thermal store combi boiler. I only pointed it out as another option. Many households are lucky if they have 25 lpm of mains cold water flow, never mind DHW. Unvented cylinders can only deliver hot water at cold mains flow rates too. The OP needs to check the mains flow rate before considering any mains pressure DHW systems.
As average mains water flow rates can provide for 2 decent mixer showers at best, anyway..... if another hot or cold outlet is opened, any system without hot and cold stored water won't cope.

I don't tend to fit Worcesters, so I'm not biased towards them. Looking at the specs, they provide 10 mins of high flow (25 lpm @ 30 degree rise) for running a bath, or for peak demands. And claimed recovery time is 13 minutes. That's possibly longer if CH is on too. They're expensive, but so are unvented cylinders.
 

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