My builder is laying a new 35mm plastic pipe from the water mains at the property's boundary to the house (a distance of about 8m). We currently have 22mm but with an odd restrictor close to the connection which looks like it is reducing it at that point to 15mm. My builder has said that he doesn't know what the restrictor is but will remove it. He said that replacing the current 22mm to a 35mm pipe will improve flow but not as dramatically as if I paid Thames Water to modify the actual connection to their mains. He said he's not authorised to touch their property.

I have had a quick look at Thames Water's website and it seems it's a lot of bureaucracy and cost to get them to do the upgrade of that bit. They do list about 150 suppliers that they have authorised to do works to their network as an alternative, but I've called about 15 of them and either they don't cover London or they don't cover individual residential properties. I will keep trying, but wondering if anyone can make a stab at whether it will actually make a huge difference, as my understanding is that my existing pressure (which is between 2.8 bar and 3 bar, depending on time of day) won't change, it's just the flow rate (which currently is about 20L per min) will improve. We are going to have an UVC. Photo below of what's installed at the moment, showing the weird 15mm narrowing (at point B), the 22mm plastic pipe we are upgrading to 35mm (at point A) and what I presume is the black outlet pipe from the Thames Water connection thing (at point C). That pipe is only about 30cm long then it hits the Thames Water connection

 

If you ask the water co to change it, I think they will increase your standing  charge.

The old pipe is likely furred up and bent anyway, so the restrictor might not be making so much difference.

12 minutes ago, saveasteading said:

If you ask the water co to change it, I think they will increase your standing  charge.

The old pipe is likely furred up and bent anyway, so the restrictor might not be making so much difference.

A company I spoke to just now says that actually all the independent contractors can do is process an application, the actual work, apparently, has to be done by Thames Water at a cost of "about £2500". So if there was an increase in standing charge as well, that would be daylight robbery squared.

My flow rate at the kitchen tap (just measured) is about 12 litres a minute. I've actually turned the stopcock down a little to deliberately restrict this, as the water was coming out of the tap too violently.

 

So, I'd say that 20l/m is pretty good anyway, and you wouldn't benefit much from the expense, unless you're filling a swimming pool, which takes days anyway. I think the benefit of changing the pipe that connects to the big mains pipe would be if it serves more than one property.

 

Also, just a thought, if you've ever fitted a monoblock tap with the copper tail pipes, you'll know how restricted those pipes seem to be (8mm pipe has less than a third of the cross section of 15mm pipe), and yet it makes no noticeable difference to the flow of water out of the tap. The water just flows faster through the restriction (although pressure plays a part in this).

Simple answer is, Yes - increasing the diameter of pipe A will increase flow and reduce the pressure drop across that section of pipe, which means dynamic pressure will be higher (static pressure remains the same, as you rightly said).

 

Edited July 22, 20215 yr by fezster
Clarified

1 minute ago, fezster said:

Simple answer is, Yes - increasing the diameter of pipe A will increase flow and dynamic pressure (not static pressure, as you rightly said).

 

Thanks. I'm already doing that: builder is only charging me £200 to do it, so it was a no brainer. He's also going to remove the weird restriction at B. My question is whether it is worth the bureaucratic hurdles and cost of getting Thames water to increase the pipe at C and it's entry point into the mains thingy, whatever that's called.

Just now, hendriQ said:

Thanks. I'm already doing that: builder is only charging me £200 to do it, so it was a no brainer. He's also going to remove the weird restriction at B. My question is whether it is worth the bureaucratic hurdles and cost of getting Thames water to increase the pipe at C and it's entry point into the mains thingy, whatever that's called.

 

Do you have a water meter? Usually, the pipework on your land belongs to you and is one side of the water meter. I don't quite understand why B and C are Thames Water's responsibility?

 

In answer to your question, you could ask TW to measure the open pipe flow rate at the boundary to get an indication if increasing the remaining pipe size would give any improvement.

3 minutes ago, fezster said:

 

Do you have a water meter? Usually, the pipework on your land belongs to you and is one side of the water meter. I don't quite understand why B and C are Thames Water's responsibility?

 

In answer to your question, you could ask TW to measure the open pipe flow rate at the boundary to get an indication if increasing the remaining pipe size would give any improvement.

I don't have a water meter - the water is unmetered, we just pay a standing charge. Technically you are probably right in that Thames Water is not responsible for anything on my land. I think my builder is just being cautious because pipe C is very short, about 30cm before it goes into public land (i.e. the Council's land, i suppose, in that it is under a pavement) so whilst he could technically replace most of that as soon as he crosses the boundary he is nervous and for some reason he is not keen even to replace that last 30cm. Maybe I should tell him I'm not happy and that we agreed the £200 would be to replace my pipe and that that black bit is my pipe as well.

6 hours ago, hendriQ said:

as my understanding is that my existing pressure (which is between 2.8 bar and 3 bar, depending on time of day) won't change, it's just the flow rate (which currently is about 20L per min) will improve.

 

You can get improvements in pressure. Not the static pressure, that won't change, but the pressure in your house at a set flow rate can improve. 

 

So for example suppose your static pressure is 2.8-3 bar and your open pipe flow rate is 20L/min. Then the pressure at say 10L/min can improve. Likewise the flow rate you can draw before the pressure falls below say 2 bar can increase. 

 

How and where was your 20l/min measured?

 

20l min wouldn't be so bad where I am. Last place only just got 10

3 hours ago, Temp said:

 

How and where was your 20l/min measured?

 

 

Kitchen tap, which was at the back of the house, although now that we have extended it the new kitchen tap will be even further back, so about 4.5m further away from the mains supply - although that's probably only a relevant consideration for cold water given that before we didn't have an UVC, just a combi boiler, and now we will have a UVC that will store all hot water in the loft.

Shouldn't you measure off a garden tap? I thought appliance taps were restricted nowadays?

Ideally you would turn on all taps that are mains fed at same time (even hot taps if you have a combi). Measure flow rate at each and add them up. Still won't be measuring the max available from the main but about as close as you can get.

 

 

11 hours ago, Temp said:

Ideally you would turn on all taps that are mains fed at same time (even hot taps if you have a combi). Measure flow rate at each and add them up. Still won't be measuring the max available from the main but about as close as you can get.

 

 

Unfortunately it wasn't really possible to do this and get a reliable reading. We bought a house that was in a really terrible condition. We knew the plumbing was awful because although the kitchen tap gave a pretty decent 20L/m, almost every other tap in the house gave much less than that (this is only measuring one tap at a time) and there was even one tap on the first floor that literally gave a drible. Our pre-purchase survey had concluded that much of the electrics were incorrectly installed and identified various damp issues, at least one of which was caused by a suspect leaky pipe. So we always knew the plumbing was awful and we needed to redo all of it. So I actually only took a pressure measurement after all taps in the house (together with the plumbing) had been removed.

17 hours ago, Oz07 said:

Shouldn't you measure off a garden tap? I thought appliance taps were restricted nowadays?

I also took a reading from the garden tap and I think it was similar. There is now just one tap in the hole property, effectively the mains pipe, but prior to A, B above being upgraded. I will do another bucket test and see what the flow rate is.

If incoming DCW is 22l/min and you're expecting DHW of 18-19l/min then you may have a problem.

 

What are your blended flowrates?

 

What are the DHW and DCW flowrates needed to meet these?

 

DCW temp varies. Assume 10C. Blended temps vary. Assume 40C. DHW production temps are flexible. Assume 45C for HP or 55C for gas. (being conservative)

 

40C shower uses about 86:14 in HP scenario or 66:33 in gas scenario. So you have enough DCW to satisfy your wishes or would you be putting in DHW capacity that goes unused?

 

https://www.spiraxsarco.com/resources-and-design-tools/calculators/water-mixing/water-mixing

 

 

 

Central cylinder and system boiler will work well. Resist temptation to run any 22 mm anywhere though (except perhaps the bath IF you have bath fill fixtures capable of high flowrates)

 

AECB water standards a good one to aim for / tell you what dead legs are. 15 mm pex is usually the answer to everything.

Sorry replied to wron thread in a different tab!

Interesting thread. We have an old supply to our site on 22m poly pipe with pretty good pressure - not measured flow rate yet. Builder suggested to get 32m supply run in for UVC. Cue Thames Water who came in last week, said existing supply pre-dated them taking over network and couldn’t say anything about the connection to the village main. They advised a new 32mm connection to the main and to disconnect the old one  - and get this - the quote is £6k! The main runs the other side of the road and my guess is traffic lights and the whole piece. So decision time for me, Having read this thread am going to measure the flow rate before accepting TW quote. If I stick with existing we will be running 32mm from the meter about 20m down the drive to the house stopcock.  By the way, measure flow rate with a bucket and stopwatch? Or is there a more accurate way?

Edited July 25, 20215 yr by Oldsteel

chop the restrictor out, do the rest in 32mm, and you'll  be happy I'll bet.

6 hours ago, Oldsteel said:

Interesting thread. We have an old supply to our site on 22m poly pipe with pretty good pressure - not measured flow rate yet. Builder suggested to get 32m supply run in for UVC. Cue Thames Water who came in last week, said existing supply pre-dated them taking over network and couldn’t say anything about the connection to the village main. They advised a new 32mm connection to the main and to disconnect the old one  - and get this - the quote is £6k! The main runs the other side of the road and my guess is traffic lights and the whole piece. So decision time for me, Having read this thread am going to measure the flow rate before accepting TW quote. If I stick with existing we will be running 32mm from the meter about 20m down the drive to the house stopcock.  By the way, measure flow rate with a bucket and stopwatch? Or is there a more accurate way?

That's interesting @Oldsteel. It really daylight robbery. Reminds me of the silly fees the council charge to run a dropped kerb application consultation. How long did it take from first submitting your application for a quote and Thames Water quoting? And did you go via Thames Water direct to get a quote, or go via a third party?

I had to make a new connection 1km away. I needed up with a 60mm pipe (by mistake) should of been 50mm. However the water board still connected it with a 32mm restrictor to the mains pipe. I called the board and said that’s the calcs and wouldn’t entertain the idea of something bigger. 

Edited July 26, 20215 yr by gc100

11 hours ago, hendriQ said:

That's interesting @Oldsteel. It really daylight robbery. Reminds me of the silly fees the council charge to run a dropped kerb application consultation. How long did it take from first submitting your application for a quote and Thames Water quoting? And did you go via Thames Water direct to get a quote, or go via a third party?

Direct to TW via their website. Their service is pretty good, you need to pay about £100 for the survey but they respond within a week and keep you informed. 

On 22/07/2021 at 12:53, hendriQ said:

My builder is laying a new 35mm plastic pipe from the water mains at the property's boundary to the house (a distance of about 8m). We currently have 22mm but with an odd restrictor close to the connection which looks like it is reducing it at that point to 15mm. My builder has said that he doesn't know what the restrictor is but will remove it. He said that replacing the current 22mm to a 35mm pipe will improve flow but not as dramatically as if I paid Thames Water to modify the actual connection to their mains. He said he's not authorised to touch their property.

I have had a quick look at Thames Water's website and it seems it's a lot of bureaucracy and cost to get them to do the upgrade of that bit. They do list about 150 suppliers that they have authorised to do works to their network as an alternative, but I've called about 15 of them and either they don't cover London or they don't cover individual residential properties. I will keep trying, but wondering if anyone can make a stab at whether it will actually make a huge difference, as my understanding is that my existing pressure (which is between 2.8 bar and 3 bar, depending on time of day) won't change, it's just the flow rate (which currently is about 20L per min) will improve. We are going to have an UVC. Photo below of what's installed at the moment, showing the weird 15mm narrowing (at point B), the 22mm plastic pipe we are upgrading to 35mm (at point A) and what I presume is the black outlet pipe from the Thames Water connection thing (at point C). That pipe is only about 30cm long then it hits the Thames Water connection

 

That is not a restrictor, in a sense that it was installed to restrict, but yes it will be causing a restriction. That is just a piece of the old copper pipe which someone has left because they didn't want to interfere with the valve, didn't have the right coupling etc. etc. 

 

 

 

 

 

Renew as much of it as you can. 

So I meaured my flow rate from the old existing mains connection (that TW want nothing to do with) and its 28 l/m. Good enough I think to pressurise the whole house? Or is ot £6k to run in a new main? I know I would rather not spend £6k on water at this stage. The extras are already starting to build ...