How many pipes will go to the gas system boiler?

[sallyjc]

Morning everyone

I am in the middle of refurbishing my house and need some plumbing advice please!

My plan is to fit a new gas boiler and an unvented hot water cylinder in the loft. All the work will be done by a qualified plumber of course - not by me! But for now I need to know how many copper pipes (and what size) will be coming down from the loft to the first floor, and then down to the ground floor.

This is so I can work out how much wall/room space I need to run these pipes down. Here is a list of all the things that will will need water!

LOFT
Gas boiler & unvented hot water cylinder

FIRST FLOOR
a) 6 radiators (including one towel radiator) connected via a "22mm flow and return system"
b) Bathroom with a sink, bath, shower, toilet

GROUND FLOOR
a) Underfloor heating with the manifold on the ground floor as well (no radiators)
b) Kitchen with a sink, washing machine, dishwasher
c) Small toilet with a sink
d) Outside tap

Ideally I would like to avoid boxing in all the pipes in a corner of the room, but I suppose it will all depend on how many pipes there are!

If I did not box the pipes in, and instead laid them side by side on the wall, would they take up a very wide area?

Thanks very much!!

Sally

 

[OwainDIYer]

Gas in a ventilated duct **
Cold feed.
Radiator flow and return (first floor) ** -- exactly where you split these two depends on
Underfloor flow and return (ground floor) ** -- where you put your zone valves
Hot to taps.
Boiler condensate to drain
Boiler pressure relief discharge to open air safe location * -- these may be able
Unvented cylinder pressure relief discharge to open air safe location * -- to share

* will be sized according to the manufacturers' instructions and the Water Regulations
** will need to be calculated by the Gas Safe installer or the heating engineer

 

[oldbuffer]

The following comments are for guidance. They are not specific suggestions, and you would need a site survey and a much better definition of the type of systems you are going to install.

A. UP to the boiler and unvented HWC:
A1 Gas pipe - diameter will depend on boiler and distance / bends from meter. Allow for 28mm, next size up is 35mm.
A2 Incoming cold water main. Probably get away with 15mm but 22mm would be better.
B. DOWN from Boiler and HWC:
B1. Pressure relief pipe. Probably straight out of loft and if so not an issue. 15mm pipe.
B2. Condensate pipe. Will need to go into the sewer system, so probably down to first floor and into soil stack at 1st floor level. If all internal and reasonably short run, 21mm plastic pipe. If longer run allow for 32mm plastic pipe.
B3. Unvented cylinder discharge pipe (D2) - probably straight out of loft. At least 22mm, could be 28mm if long run.
B4. Radiator flow and return. Down to 1st floor. Allow for 22mm pipe for each.
B5. Bathroom cold supply. If coming off control group (balanced pressure) one pipe, 22mm would fill the bath faster but 15mm might do.
B6. Bathroom hot supply. 22mm.
B7. Separate flow and return to UFH on ground floor if to be on a separate zone, otherwise continuation of radiator flow and return. 22mm.
B8. Cold water service to ground floor (except kitchen sink) - as B4.
B9. Hot water service to ground floor - as B5.
B10. Kitchen sink, and possibly outside tap, should be taken from incoming mains supply to property.

In terms of space, you need to allow for pipe diameter, diameter of insulation where required (hot pipes, cold pipes if running in cold areas), pipe clips and some spacing between pipes, particularly between hot and cold. Perhaps work on the following:
1. 15mm pipe - insulated. 15 + (2 x 19) + 10 = 63, say 65mm.
2. 22mm pipe - insulated. 22 + (2 x 19) +10 = 70mm
3. 28mm pipe - insulated. 28 = (2 x 19) + 10 = 76mm, say 80mm.
4. 15mm pipe - clipped but not insulated. 15 + (2 x 5) + 10 = 35, say 40mm.
5. 22mm pipe - clipped but not insulated. 22 + (2 x 5) +10 = 42, say 45mm.
6. 28mm pipe - clipped but not insulated. 28 + (2 x 5) +10 = 48, say 50mm.

Items 1 to 3 assume 19mm thick insulation, which probably doesn't meet building regulations, but not by much, and it is what is mostly used.

 

[sallyjc]

Hello there and thank you both for the fantastic replies!

Oldbuffer I would be grateful if I could you ask a few more questions please?

A1 - the gas pipe will run up the outside of the house wall and will enter the loft exactly where the boiler will go. This is because my house has an outside gas meter box and is pretty much in line with where the boiler will go, so it should be nice and easy.

A2 - I think my water main pipe might be 15mm, at least the bit that pokes out of the floor is 15mm (the house was built in 1970). I am hoping my mains water is strong enough for me to have an unvented hot water cylinder so I have bought a flow measuring cup and a pressure dial from Amazon and will check what my flow rate and pressure are. Assuming the numbers are OK, should I still ask the plumber to increase the pipe size from 15mm to 22mm for it's journey up in to the loft?

B1 - when you say "straight out of the loft", do you mean out through the wall in to the outside world, or do you mean down in to the room below on the first floor (which is the bathroom by the way). If you mean the pipe should go straight through the wall in to the outside world, where does it go next? Thanks.

B2 - I am lucky in that the soil stack is very close to the boiler - just on the other outside of the wall. So can this 21mm plastic pipe connect straight in to the soil stack?

B3 - when you say "straight out of the loft", do you mean out through the wal in to the outside world, or do you mean down in to the room below on the first floor?

B5 - I would like the bath to fill up faster thanks!

B7 - if by separate zone you mean the underfloor heating could be turned on while the upstairs radiators are turned off, then that is what I would like. So I will therfore allow for two 22mm pipes.

Thank you so much for your help. This is exactly what I need to know, how much space I need to run all these pipes!

Best wishes

Sally

 

[Madrab]

I think my water main pipe might be 15mm

Hopefully not as that will struggle to satisfy all your cold water needs and an un-vented cylinder quietly, it just can't pass enough volume of water per min if several outlets are calling for cold water at the same time as well as suppling the hot.

Start with checking the mains, you're looking for at least 20 L/Min @ 3 bar dynamic (in your case if it's 15mm, run a few cold outlets at the same time to check max dynamic flow).

 

[sallyjc]

Hi Madrab

I will let you know what figures I get (I am still waiting for the measuring devices to be delivered).

In terms of water flow, I am not very demanding. It's just me and two young children in the house and there is only one bathroom. I have a shower in the morning when they are asleep, and I have a bath in the evening when they are asleep, so there is no one awake to fiddle with the taps downstairs!

Also I don't really want to upgrade the mains water pipe unless it is 100% necessary - as I am guessing it will be expensive!

Thanks

 

[oldbuffer]

A1. Gas pipe sizing must be done by the boiler installer. However, from your description 22mm would probably be sufficient. If you are not fortunate enough to live in a low crime rate area, consider having the outside run in 3/4" steel pipe, as it is less attractive to thieves than copper. You can't use plastic pipe.
A2. If any part of your cold pipework is 15mm, there is no point upgrading to 22mm thereafter. Your pressure checks should be made as both static (pressure gauge attached to an open tap with no water flowing) and dynamic, with the gauge attached and another tap running. If you use the kitchen tap and an outside tap to do these tests, make sure there are no restrictive isolation valves (not including your stop valve or one in your water meter) between the incoming main and the outlets. Full bore valves are OK.
B1. Straight out through the eaves (most likely) and terminating against an outside wall just below.
B2. Should be OK to terminate straight into stack provided boiler has an internal trap to avoid sewer smells coming in. Otherwise a running trap would probably do.
B3. Again, straight out through the eaves. Its a while since I did one, but I think you can terminate facing a wall provided there is no risk of scalding to anyone. Check with your installer.
B5. You won't get the hot water out faster than it can be replaced by cold, so if you have only a 15mm incoming cold there would be little point going to 22mm for hot, unless to allow for future improvements.
B7. That is what I meant by zoned.

If it is just yourself and two children in the house, and you appear to have little requirement for simultaneous hot water use which cannot be managed by yourself, you might wish to consider a combi boiler and forego the extra complication and expense of an unvented hot water system. Pipework layout would be pretty much as described in my previous post. If, as the children grew, you had a need for more hot water on tap, you could implement the unvented solution using the same boiler. Combi boilers can be used to heat any indirect (vented or unvented) hot water cylinder.

 

[sallyjc]

Hi Oldbuffer

Thanks for the reply, and yes sadly there is crime in my area. I am therefore thinking of disguising the three copper pipes (gas, pressure relief pipe, and unvented cylinder discharge pipe) by running them down the side of the house within black plastic pipe - next to the soil pipe, and so it won't been seen. I hadn't thought about the crime risk until you mentioned it.

I had a combi boiler in my last place and the flow out of the shower was miserable. I am sure it could have been due to other things, but whenever I stay at my sister's (who has a Megaflow) I can't believe the pressure! Plus a few years down the line I might install an ensuite which should work well with an unvented cylinder. And if I have to upgrade the mains water pipe in the future I will do it, I just can't afford it at the moment

Good night

 

[Madrab]

In terms of water flow, I am not very demanding.

It's not about that @sallyjc, it's about what the min your un-vented cylinder needs to be effective. There's no point in spending hundreds of pounds only for the un-vented not to do it's job properly. Your sister may have the supply to give her that fabulous pressure/flow, you need to establish if yours can do the same.

A good combi can easily give you great shower pressure and flow if used alone and may be a better option. I would suggest a professional be brought in to give you the options

 

[sallyjc]

Hi Madrab

Thanks for the reply.

Regarding a combi boiler, what flow rates are possible (the higher the better!)? I imagine it will depend on my mains flow/pressure? But for arguments sake let's say I was getting 25 litres a minute at the tap, could I hope to achieve that at the shower head? Hope to confirm my figures soon (once Amazon has delivered my measuring devices!).

Thanks

 

[sallyjc]

Good morning

Sorry to come back so soon with more questions, but I do like the idea of a combi boiler. I had originally ruled one out due to bad experiences at my last two properties. But if there are large flow rate models on sale then my problems could be solved!

I have done some more Internet research and have come across the "Mira Platinum Dual Ceiling Fed - High Pressure / Combi Boiler". I recognised the buttons immediately as I used one last year while staying at an Air B&B. They are amazing and easily the best shower I have ever used So I would like one, and can maybe forget the Megaflow which I only ever wanted for the shower, and not because I had multiple bathrooms.

However I have a question that concerns my bath and please allow me to explain. The Mira shower can provide water to a ceiling shower and also a hand held shower (I am sure you all know this already!). I only need the ceiling shower so I am thinking could I instead direct the water to a nearby bath via this second connector/valve? The bath will be freestanding and my original idea was to fit taps on to the wall. But if I could use the Mira system instead then I would only need a spout on the wall for the bath. However I am a bit worried about the flow rate, i.e. if the ceiling shower was turned off would the bath still take a long time to fill up if the water was coming through the Mira unit, instead of coming straight from the combi boiler?

Thanks and sorry for all these questions!

 

[Madrab]

You'll be struggling to get 25L/Min from a 15mm pipe not unless the cold mains sounds like a hose when it's running. No - flow rate is governed by the the throughput of the boiler. A figure of 13-14L/Min is easily achievable if you go for a larger Combi 32Kw+.

I rate a good shower at at least 15L/Min combined @ mains pressure. That would give you a good shower but it depends on the shower head, shower type etc too but a good combi/cold mains could deliver that without issue.

Jings, one of those showers could probably pay for most of a cold water upgrade on its own

It's only 16L/Min though so if that's good enough for you then a good combi could fulfill that without issue I would think

yes as far as flow rate to the shower head .... any combi fed outlet can take a while to fill a bath, especially from a shower.

 

[sallyjc]

Hi Madrab

Thanks for the reply.

I've been doing some more reading/thinking. 15 LPM would be fine for a shower but my bath is quite big (250 Litres), and this would mean it would take roughly 17 minutes to fill up, which is probably a bit too long. I know, First World problems! Actually it would probably take longer as I like my baths quite hot, and I imagine the 15 LPM rating/figure would keep on dropping?

So maybe I'm leaning back towards an unvented hot water cylinder again! I am thinking a cylinder will give me the best of both worlds though, an invigorating shower AND a faster bath fill. Of course I imagine it will all depend on my mains flow/pressure. I'm aiming to measure all this tomorrow and will report back

Thanks

 

[sallyjc]

Morning all,

I have done all the measuring now. The pressure dial says 3.25 BAR when the mains stop cock is 100% open. Also the flow rate seems very fast. The measuring cup I bought goes up to 22 LPM, and the water just gushes out at the maximum reading. So (with a little help from my Dad!) I checked by filling up a 10 LITRE bucket which took about 28seconds, maybe a little faster.

So am I therefore OK for an unvented cylinder then? As I said before, I only have one bathroom and nobody else will be using taps when the shower or bath are running.

Thanks very much

 

[ianmcd]

yes