Upgrading water supply to improve flow to property

Participant · 3 Feb 2016 at 20:45

Hi all

We have a 10 year old Ravenheat combi boiler and and the water supply comes in through 15mm copper. We're finding the hot water system insufficient for us, having a young family with high concurrent water demands.

The house is a 4 bed 3 bathroom property, and we're finding the extra bathrooms almost pointless as two people can barely run a tap at the same time for the impact it has on the other's flow, let alone shower at the same time.

I'm therefore considering tackling this in two ways:

1. Upgrade water supply to property to 32mm MDPE from the pavement stopcock to the interior stopcock. Not sure what if anything they can do to the communication pipe...

2. Upgrade combi to a powerful system boiler with good recovery rates, in conjunction with a 300L Megaflo cylinder.

I've got Severn Trent coming out to inspect the site and advise on installation and lead (house was built in 1960), as well as a plumbing company coming out to quote for the entire job.

My questions are:

1. Has anyone else here undertaken such a project, and do you have any advice? Initial indications from Severn Trent are that their part of the job would cost thousands.

2. What are these things in the pavement? The first one just looks like the stopcock, but what does the pipe look like to you? The second - no idea what this is, but the hatch has water company markings on it.

3. Both the above hatches are visible in this picture.

The wall on the right is our garage, where I want to put the cylinder, which is on the opposite side of the house to where the current water supply enters the property. This means I need to move the water meter and internal stopcock.

Crude diagram of our property and key locations in the plan:

I know that the trench has to be >750mm deep, inspected by the water company, etc. Many thanks for any advice about what this job might involve!

Al-Ectrician · 3 Feb 2016 at 20:56

Have you measured the flow rate of cold at various points ?
Have you measured the standing and dynamic pressures ?
Has the stop valve in the driveway been checked fully opened position ?

I would investigate all possibilities for your own peace of mind.

If you could increase cold flow rates then possibly a higher kW rated boiler would help to supply multiple outlets.

HTH
Alan

craig_t · 3 Feb 2016 at 21:09

The water company should own it up to your property boundary, so ask them first and get some advice they'll tell you exactly what you need.

I asked the very same thing, for the same reasons. So you just dig the trench to your property boundary and they come do the rest and connect it in.

Participant · 3 Feb 2016 at 21:11

Thanks.

Flow rate at garden tap is 18L/m.

I haven't measured pressures, but the plumber will do this tomorrow when they come to assess the job. Severn Trent guarantee 1.5 bar in my area.

I have not checked the stop tap as I'm not certain that the one I've photographed is mine, but visually it looks fully open, right? They're 90 degree taps as I understand it.

So if I do the digging on my property they'll dig up the pavement as part of the fee? What if the communication pipe from the external stopcock to the water main is crap? Am I screwed?

Dangerous Dave · 3 Feb 2016 at 21:18

As mentioned by Al-Ectrician, have you had the static pressure and dynamic pressure (pressure at one tap when another is running) measured ?

no point in upgrading the pipe work if you are getting 1 bar which is the minimum the water company has to provide, you ideally need 3-4bar for an unvented cylinder.

EDIT Just seen the update, you ideally want the pressure measured at the stopcock before you proceed as 1.5 bar wouldn't be enough for an unvented cylinder. Your other option is an accumulator, effectively a large pressured cold water tank that holds several 100 litres of water to compensate for poor mains flow/pressure.

Participant · 3 Feb 2016 at 21:45

Cheers. Hoping the pressure exceeds this quoted 1.5 bar but we'll see. Plenty of room for an accumulator if required, though 60L/m at 1.5 bar would surely be ok? 32mm plastic would easily provide this flow rate.

Dangerous Dave · 3 Feb 2016 at 21:49

Participant said:
Cheers. Hoping the pressure exceeds this quoted 1.5 bar but we'll see. Plenty of room for an accumulator if required, though 60L/m at 1.5 bar would surely be ok? 32mm plastic would easily provide this flow rate.

You ideally want to be able to provide around 1bar to each running outlet, if you want to have two showers running simultaneously you are going to need 2bar+ as most high pressure mixer showers are 1bar minimum.

Windle · 3 Feb 2016 at 23:26

2nd pic is a valve on the water main

justalex81 · 3 Feb 2016 at 23:37

As said the water company will only get you to the boundary of the property. you'll then have to dig the trench and lay the pipe yourself.

Sometimes its cheaper to put an insulated and screened water tank in the loft and fit a booster pump to it.

Also get a gledhill cylinder instead of megaflow. save yourself about £400

Derek W · 4 Feb 2016 at 08:28

Windle said:
2nd pic is a valve on the water main

I'd agree with this, stw southern Trent water, sv stands for sluice valve.https://en.m.wikipedia.org/wiki/Gate_valve

ironhorse · 4 Feb 2016 at 15:18

15mm copper supply to boiler sounds strange, I thought 22mm supply was the standard?

marmalade · 4 Feb 2016 at 17:18

Ravenheat combi a boiler that most plumber laugh/avoid. Get a Vaillant or Worc/Bosch. If you change you will need large hot water tanks. Make sure you have the meaty rafters/walls to take the weight and plan your pipe runs. I love combi boilers just about to change a Vaillant 27 years old never had a fault. The new condensing boilers will not last nearly as long. /Your house looks new so should be in standard 25mm blue plastic -will increasing the size be worthwhile? In Sydney our water pressure is so high we have to deal with Hammer. Hope you get a good plumber

Entropy · 4 Feb 2016 at 18:06

As far as i was aware water companies are obligated to connect a replacement pipe free of charge if the current one is lead. You have to do all the ground works and plumbing works up to your property boundary. They then come and dig out around the stop tap and connect up the new supply pipe whilst disconnecting the old one. They tend to run on 25mm MDPE, 32mm will likely incur a charge if possible.

Participant · 4 Feb 2016 at 20:47

Guys, really appreciate all the replies. Very useful.

To answer some specific points:

- A company came out to survey and quote tonight. They measured (unprompted) the flow, and static and dynamic pressures. The result came out as 18L/m at 2 bar dynamic, 4 bar static.

- Thanks for clarifying what the second valve is. I'd assumed the main would be in the middle of the road rather than that pavement...makes sense for it to be in the pavement though.

- The company agreed with justalex81 and said that I might as well go for a cheaper cylinder than Megaflo, since ours is going in the garage and there's plenty of space for a separate expansion vessel, which is apparently the main differentiator between Megaflo et al. He's going to provisionally spec me a Worcester Bosch unvented. Obviously I'm aware that he's incentivised by WB to spec WB products, but if it saves me money vs. Megaflo that's fine by me. He's happy to fit whatever I want though, so if Gledhill is significantly cheaper, I'll go for that.

- 15mm is my best guess based on me being able to see approx 5mm of pipe before the stopcock due to the screed under the sink in my utility room. It could be that it's fatter, but 4bar and only 18L/m tells me it's probably a pretty small pipe. 22mm might be standard now (I think new builds probably have more than this), but it's a 1960 house.

- marmalade - he smirked as soon as I told him it was a Ravenheat. They all do. I'm going to go for a Worcester Bosch...he seemed to think a 30Kw Greenstar 30i (30CDi at the most) was all we needed. As mentioned it'll be a 300L cylinder on a concrete garage floor, so no concerns with floor support. It looks new from the picture because that was an extension done by the previous owners in 2007.

- I called the water company today and speccing 32mm over 25mm will mean two things:

1. Higher standing water charge (insignificant)
2. One off meter upsize fee (~£180).

Anyway the company is putting a quote together and I liked what he had to say. Lead assessment and new supply survey is happening over the next week.

Thanks again!

NoNameNoNumber · 4 Feb 2016 at 22:26

I'd be interested to hear what they say about the lead pipe. I asked when I had a meter put in about replacing the lead pipe but the fitter said not to bother, my pressure isn't amazing though so I is something I have been thinking about doing myself...

robj20 · 5 Feb 2016 at 07:08

I need to get them out to ours at some point to check pressure, flow and if there is any lead.

Dangerous Dave · 5 Feb 2016 at 09:56

A 30kw boiler will probably be to big for your property, you should run your house details through a heat loss calculator. You will probably find 15-18kw will be big enough if the house has good insulation etc.

http://calculators.baxiknowhow.co.uk/boiler-sizing/

For efficiently you want a boiler that has a low minimum kw output so that the boiler can run on the minimum burn rather than cycling on and off when it can no longer dissipate the heat it is producing.

Most people look at the maximum which the boiler will be running at for a small amount of time, you want a boiler that can modulate down as far as possible this means picking a boiler that is the right size for the property as a 30kw can't modulate down as far as a 15/18kw boiler. You do also need to take into account the coil size in the cylinder if the boiler output is under this it will take longer to heat.

I would go for weather compensating controls to allow the flow temperature to be modulated depending on the outside temperature. This allows the return temperature to be as low as possible. Condensing boilers only condense when the return temperature is under 56c, if you have the flow temperature set at 70-75c, like many older systems run at, the return temperature will be over 56c and the boiler will never condense.

I found http://www.diynot.com/diy/forums/plumbing/ a good resource when researching my new system. If has a lot of repair/installers who give good advise, you might want to do a little research on boiler brands as they don't rate the newer Worchester boilers due to many parts being plastic/rubber compared to metal on other brands.

Skiddley · 9 Feb 2016 at 15:10

25 is standard. I asked for a 32 under the lead pipe replacement scheme for our place to improve pressure and was knocked back, unless I paid $$$. 25mm was FoC.

rah^ · 9 Feb 2016 at 19:14

25mm with decent pressure in the host main is more than enough.. but as its Severn Trent I suspect they are still aiming for 2bar in the host main so!

From memory Thames now fit 32mm as standard (at least in London)

also changing the size wont change the pressure but you would get more flow down it to the kitchen tap

Participant · 10 Feb 2016 at 13:23

NoNameNoNumber said:
I'd be interested to hear what they say about the lead pipe. I asked when I had a meter put in about replacing the lead pipe but the fitter said not to bother, my pressure isn't amazing though so I is something I have been thinking about doing myself...

The fitter said not to bother?! Why would he say that and why would you then listen to him?

A) it's arguably dangerous and B) the flow rates with old lead are poo.

Dangerous Dave said:
A 30kw boiler will probably be to big for your property, you should run your house details through a heat loss calculator. You will probably find 15-18kw will be big enough if the house has good insulation etc.

http://calculators.baxiknowhow.co.uk/boiler-sizing/

For efficiently you want a boiler that has a low minimum kw output so that the boiler can run on the minimum burn rather than cycling on and off when it can no longer dissipate the heat it is producing.

Most people look at the maximum which the boiler will be running at for a small amount of time, you want a boiler that can modulate down as far as possible this means picking a boiler that is the right size for the property as a 30kw can't modulate down as far as a 15/18kw boiler. You do also need to take into account the coil size in the cylinder if the boiler output is under this it will take longer to heat.

I would go for weather compensating controls to allow the flow temperature to be modulated depending on the outside temperature. This allows the return temperature to be as low as possible. Condensing boilers only condense when the return temperature is under 56c, if you have the flow temperature set at 70-75c, like many older systems run at, the return temperature will be over 56c and the boiler will never condense.

I found http://www.diynot.com/diy/forums/plumbing/ a good resource when researching my new system. If has a lot of repair/installers who give good advise, you might want to do a little research on boiler brands as they don't rate the newer Worchester boilers due to many parts being plastic/rubber compared to metal on other brands.

Thanks for this. 30Kw may be too big, but I'd rather go too big than too small, especially since according to the spec sheets boilers like Worcester's Greenstars can modulate down to at least as low as their junior boilers?

Will definitely spec weather compensation.

Yep done a lot of reading on DIYNot and it's a good resource. I've heard that WB aren't necessarily as bees-knees as they were once considered, but for simplicity, compatibility, and the epic warranty, I'm probably going to go Worcester boiler, cylinder, and controls.

Skiddley said:
25 is standard. I asked for a 32 under the lead pipe replacement scheme for our place to improve pressure and was knocked back, unless I paid $$$. 25mm was FoC.

Yep, if my choice is free 25mm vs. £££ 32mm, I'll go 25mm. But I'm not even sure my service or communication pipe is lead anyway, so I think my choice will be £££ for 25mm or £££ for 32mm, in which case 32mm is a no-brainer.

rah^ said:
25mm with decent pressure in the host main is more than enough.. but as its Severn Trent I suspect they are still aiming for 2bar in the host main so!

From memory Thames now fit 32mm as standard (at least in London)

also changing the size wont change the pressure but you would get more flow down it to the kitchen tap

Yeah we've got 4 bar static, confirmed by two plumbers. Not bad I guess! Increasing the pipe cross-sectional area won't change static pressure but it can improve dynamic pressure I believe.