Upgrading pipe sizes

[fezster]

So I'm about to have my hot and cold water pipes upgraded from 22mm poly to 28mm copper. This is to resolve the flow restriction to multiple shower outlets. There's approx 15m of pipe for each hot and cold leading to the bathrooms which will all be upgraded to 28mm. However, the megaflo inlet and outlet remain at 22mm. My understanding is that this is fine - the increase in pipe size anywhere on the circuit will reduce the overall pressure loss and increase the flow - can someone please confirm this for me?

I also have the option of having my megaflo 22mm PRV replaced to a 28mm, as well as a small section (maybe half a metre) of 25mm MDPE upgraded to 32mm MDPE. My incoming main is 32mm MDPE. It sounds like the effect of these would be negligible if what I assumed above is correct, but again, any pointers, as having it done all at once would be more cost effective. My water softener is 22mm (high flow kit), but is stated to work at 54 l/min, so this would remain straight after my mains anyway.

Thanks!

 

[Pro Action]

Yes increasing the hot and cold supplies from 22- 28mm should help to resolve the drop in flow rate when using multiple shower outlets provided the flow from the incoming mains supply is sufficient and the water softener isn't reducing the flow which it shouldn't if it works at 54 L/min.
What flow do you have on the incoming mains?
Also test all of the shower outlets with the softener bypassed to see if this is making a difference.
Another option would be to run separate hot and cold supplies in 22mm to each shower.
If you do increase to 28mm you should have a bronze pump for a secondary hot water supply.

 

[SimonG]

Can only confirm the increase in water wasted waiting for hot water. Without seeing whats what.

 

[ShaunCorbs]

also if you havent put a secondary return in

 

[macackau]

Your incoming mains flow rate is the most important thing here, no point upgrading if you're only getting 15 litres a minute, I imagine with a 32mm MDPE it is quite substantial though.

 

[Ch4 plumbing]

Your incoming mains flow rate is the most important thing here, no point upgrading if you're only getting 15 litres a minute, I imagine with a 32mm MDPE it is quite substantial though.

Spot on, check your incoming water main dynamic flow rate first before spending money on pipe reruns.

If you have already done this then what is it?

 

[fezster]

Last night I measured the flow rate from both outside taps running at the same time. It's hard to measure and I'll do a more substantial test (much larger bucket) on the weekend, but I achieved 25l/m from both taps (so 50 l/m) . I also measured the pressure from a washing machine outlet (after my 3 bar megaflo prv) and got just over 1 bar pressure, with both taps running. Static pressure before the prv is 4 bar.

Just now I measured the dynamic pressure on my shower hose outlet with the shower running. The gauge showed just over half a bar. This ties in with the showers MI which quotes 16 l/m at 0.5 bar. Static pressure at the shower is 2.5 bar.

Am I right in saying that increasing the pipe diameter will lower the pressure loss and give a greater dynamic pressure at the shower?

 

[fezster]

And yes, plan is to run a 22mm secondary return at the same time and fully insulate all hot pipes.

 

[rpm]

Last night I measured the flow rate from both outside taps running at the same time. It's hard to measure and I'll do a more substantial test (much larger bucket) on the weekend, but I achieved 25l/m from both taps (so 50 l/m) . I also measured the pressure from a washing machine outlet (after my 3 bar megaflo prv) and got just over 1 bar pressure, with both taps running.

Unless I`m missing something all your flow rates are now reduced from what you said before, am I missing something and apologises if I am.

 

[SimonG]

22 secondary return. Oh dear.

 

[macackau]

50 l/m and you are having issues with the flow rate with multiple outlets open? Something isn't right here. I don't think it's a pipe upgrade needed. I have several customers with 25 or 32mm MDPE and the rest of the house is all piped in 22mm copper and they have no drop in flow with multiple outlets open. Are the garden taps fed off the balanced supply or before it? Be good to know the flow rate after the combination valve.

 

[fezster]

Garden taps measured before 3 bar PRV.

The washing machine connector just after the PRV (from a washing machine style outlet) gave me 28 l/m.

Some more info about the pipe runs - all are 22mm poly before teeing off to 22mm copper to the showers. First shower is roughly 15m, second is roughly 25m, and last is about 30m pipework.

The dynamic pressure at the shower is what's confused me most. Only half a bar with 18 l/m being delivered. That's a 2.5 bar drop, and increase in height is only 5m (so 0.5 bar drop expected). Yet dynamic pressure at the outside tap (delivering about 25 l/m) is a 0.5 bar drop. Is the dramatic pressure drop an indication of undersized pipework?

 

[fezster]

22 secondary return. Oh dear.

This is what two different plumbers have recommended. Could you elaborate - would you expect it to be bigger? Or smaller?

 

[ShaunCorbs]

This is what two different plumbers have recommended. Could you elaborate - would you expect it to be bigger? Or smaller?

15mm will be fine as long as not stupid distance

 

[fezster]

50 l/m and you are having issues with the flow rate with multiple outlets open? Something isn't right here. I don't think it's a pipe upgrade needed.

Correct me if Im wrong here, but isn't it the dynamic pressure which is the problem, rather than the flow rate. The shower MI state 16 l/m at 0.5 bar. So even though my mains can deliver far in excess of that, isn't it the shower dictating the flow rate, because of the low pressure.

And whilst I havent measured this, with a second shower on, the dynamic pressure probably drops to a paltry 0.1/0.2 bar, and hence flow drop dramatically to both.

I'm not saying I've gotten my head around this completely, but my understanding is that if I can raise the dynamic pressure (by increasing the pipe size), then the shower will have a higher flow rate?

 

[fezster]

15mm will be fine as long as not stupid distance

It's roughly 25m to where the pipe will loop. I think this is why they said 22mm would be better, otherwise I'll need a more beefy bronze pump.

 

[ShaunCorbs]

It's roughly 25m to where the pipe will loop. I think this is why they said 22mm would be better, otherwise I'll need a more beefy bronze pump.

15mm will be fine only needs a flow and stnd 65-150 will be fine

 

[lame plumber]

try some different plumbers, yours dont seem to understand the basics of a secondary return and how it works. So the advice on increases the pipe sizing for little gain will probably be suspect as well.

 

[fezster]

Just now I measured the dynamic pressure on my shower hose outlet with the shower running. The gauge showed just over half a bar. This ties in with the showers MI which quotes 16 l/m at 0.5 bar. Static pressure at the shower is 2.5 bar.

Ok, scrap what I said here. Must have something to do with measuring gauge being on the same shower valve (gauge on hose outlet, with main shower running).

Just redid the dynamic pressure test by running a different shower. Gauge dropped from 2.5 bar to 2.1 bar. Now Im even more confused. What does this mean?

 

[macackau]

It means it's time to get someone in who knows what they are doing.

 

[fezster]

Isn't the point of this forum to share advice and knowledge so that you're better informed when you do get somebody in? Whilst I appreciate the point you are making, it's not through lack of trying on my part. I've had multiple people in, and it's possible I've been unlucky. However, the reality is probably that every person has a different solution depending on their own experience. Just as on here, some have said accumulator, some have said blockage, some have said pipe size. They're all guesses based on experience, which I appreciate, as they have given me ideas to look into. There'll be some here who understand the science behind it, and it's those I'm asking to help to explain what I'm seeing.

One of the questions I asked at the beginning of this thread is quite a straightforward one. Would 28mm pipes be beneficial even though the megaflo inlets and outlets are 22mm. Hopefully amongst all the noise about secondary returns and how incompetent the plumbers I've had so far are, somebody might be kind enough to answer the questions I raised.

 

[macackau]

Where abouts do you live? Someone on here might be able to help

 

[fezster]

I'm in se london. If there is someone, that'd be great.

I had two more guys round. Both said they'd probably upgrade the pipe size, but they couldn't guarantee it would fix it. One was very honest and said he'd recommend getting a commercial plumber as the distances are quite large. How would I go about finding commercial / semi commercial installers?

I also spoke to haetre sadia. They said this cylinder is capable of 74 l/m. They did say that it's possible the pressure reducing valve is malfunctioning and restricting flow. The problem I have with testing that is the outlets I have immediately after the prv is 15mm. It gives me 28 l/m. I don't think it's capable of delivering 50 l/m. Other than changing the prv speculatively, is there any other way of checking the flow through it?

 

[Pro Action]

I'd advise you find an unvented registered plumber to check the Megaflo installation before upgrading the pipe sizes. By law for safety purposes you must be unvented registered to work on a Megaflo.
The unvented registered plumber should also be able to help with the pipe sizing if that is necessary.

 

[fezster]

I'd advise you find an unvented registered plumber to check the Megaflo installation before upgrading the pipe sizes. By law for safety purposes you must be unvented registered to work on a Megaflo.
The unvented registered plumber should also be able to help with the pipe sizing if that is necessary.

Every plumber so far has been G3 certified. The cylinder was also serviced two weeks ago and the strainer cleaned. Thanks for the advice though.

 

[Staffy85]

I may be wrong but it sounds to me like your overall local water main pressure isn't good enough to support multiple outlets running at the same time, from post #7

" I also measured the pressure from a washing machine outlet (after my 3 bar megaflo prv) and got just over 1 bar pressure, with both taps running. Static pressure before the prv is 4 bar."

drops to just 1bar! I highly doubt upping the size to 28mm will help at all but that's my opinion and not fact...

 

[fezster]

I may be wrong but it sounds to me like your overall local water main pressure isn't good enough to support multiple outlets running at the same time, from post #7

" I also measured the pressure from a washing machine outlet (after my 3 bar megaflo prv) and got just over 1 bar pressure, with both taps running. Static pressure before the prv is 4 bar."

drops to just 1bar! I highly doubt upping the size to 28mm will help at all but that's my opinion and not fact...

Drops to 1 bar with 50 l/m flowing. I don't pretend to fully understand working pressure, but I think those are pretty good figures for multiple outlets.

However, I think the long and short of it is that even one outlet after my prv cannot deliver more than 28 l/m. I tried the washing machine pipe on its own, gave 28 l/m. Then put outside tap on (after prv) got 14 l/m on both (total 28) put the utility tap on and got 10, 10 and 8. These are all outlets after the prv and all within a few metres of it. The upstairs pipework doesn't even come into the equation. I'm more and more suspecting the prv is restricting flow.

Before my prv, one tap delivers 33 l/m and two taps deliver 50. The prv or the pipework just before and after it looks the suspect!

 

[Scott_D]

Post some pictures
Everyone is guessing based on your info and figures

 

[fezster]

Yes, of course. Here's pics going from right to left:

32mm MDPE incoming main.
Reduced to 25mm MDPE.
Reduced to 22mm copper.

Then it tee's down to the kitchen tap and outside tap.
Then the speedfit tee goes to an outside tap.
Then the water softener input and output, with bypass.

Then you have the blue isolation valve before the megaflo pressure reducing valve.
Immediately after this you have a tee going up to the balanced cold.
Then the megaflow pressure relief valve.
Speedfit reducing tee to outside tap.
There's a gate valve to isolate the megaflo input (not visible in the picture)
And you can just see the washing machine style tap before the megaflo inlet.

Hope that's useful.

 

[Pro Action]

If you are getting 1 bar working pressure on the ground floor the pressure on the upper floors is going to be less than this, so yes the working pressure could be a factor.

It's also possible that it could be a combination of factors such as pipe sizing and working pressure.

 

[fezster]

If you are getting 1 bar working pressure on the ground floor the pressure on the upper floors is going to be less than this, so yes the working pressure could be a factor.

It's also possible that it could be a combination of factors such as pipe sizing and working pressure.

See post #19. Static pressure is 2.5 bar (0.5 bar drop for 5m in height presumably), and working pressure with one shower running at 18 l/m is 2.1 bar.

 

[Scott_D]

Have you tried with the softener bypass open?

 

[Pro Action]

Is there a gate valve after the pressure relief valve?
If so that shouldn't be there, get a G3 certified plumber to remove that.

 

[fezster]

Have you tried with the softener bypass open?

Yup. Exactly the same. Softener is a Tapworks AD11 with high flow kit, so *should* be capable of 54 l/m.

 

[fezster]

Is there a gate valve after the pressure relief valve?
If so that shouldn't be there, get a G3 certified plumber to remove that.

There is. That's interesting advice - could you tell me why it shouldn't be there? And would it be causing the flow issues, or do you mean it shouldnt be there from a safety point of view? (It was the original G3 certified installer who put it there btw).

One other thing which occurred to me. I was reading the installation guide for various Reliance pressure reducing valves. They advise a minimum distance between IT and the balanced cold water take off. The instructions say this is to ensure "laminar flow". The megaflo instructions have no such advice. I wonder if my balanced cold should be slightly further away from the prv.

Edit - I see it's in the megaflo MI:

vii) No valve should be fitted between the 8 bar pressure relief valve and the Megaflo eco unit.

I wonder what the reason is though.