MDPE 32 or 25mm into the house

[seb963]

Hi,

I have just had Thames Water upgrade my mains connection to a 32mm MDPE, however my builder has run a 25mm MDPE after TW stopcock from the property boundary into the house, hence I am wondering if this would have already reduced the pressure I would have had into the house. I would have expected him to run a 32mm MDPE.
The house is now on mains pressure system (converted from gravity fed system to unvented with HW cylinder) with one bathroom, but I have the plan to add a second bathroom in the loft, and I am worried that the pressure will not be enough on the 25mm pipe. The pressure on the first floor bathroom is better than with the old gravity fed system but not exceptional.
The question is whether a 25mm is ok, or should the builder have gone for 32mm for the mains inside the house? Having paid £1100 for the TW upgrade, I want to make sure this was worth the money!
For reference the flow at the cold tap in the kitchen is about 10L/min, and reduces to 6L per min when all cold taps are opened at the same time (bath, bathroom tap, kitchen tap)

Regards

Matt

 

[ShaunCorbs]

you have a bigger problem if your only getting 10lpm (mains water) for an unvented system you need upwards of 25lpm

also what did thames water say your max/ min pressure or flow rate was?

 

[Dotty]

It won't reduce the pressure but it will reduce the flow rate as above.

What did the builder specify in his written quote?

Though you should really have employed a plumber......

 

[seb963]

I have measured it myself (probably not very well!) by filling in a 1l bottle in 6 seconds... TW did not mention the max pressure

 

[ShaunCorbs]

sounds like either wrong system if tw can only supply you with what your getting or right system depending on what tw can give you could be a half shut valve or a few things that will reduce your flow

 

[mfgs]

What flow rate did you have at the kitchen sink before the upgrade?

 

[seb963]

I had about 6L per min from memory

 

[ShaunCorbs]

I had about 6L per min from memory

are you sure you have an unvented cylinder and not a cylinder with a tank in the loft / above it ?

 

[joni os]

Length of 25mm MDPE is a factor. Thames Water should be able to confirm pressure at their meter, expect 3 bar+, but flow through meter also important. Not unknown for faulty meter to restrict flow if upstream works were not properly cleansed. Your meter may be 3/4", changing to 1"will increase flow.
OP is silent regarding upgrade of internal pipework, new stopcock and feed to unvented should be sized to suit.

 

[Dotty]

I have measured it myself (probably not very well!) by filling in a 1l bottle in 6 seconds... TW did not mention the max pressure

About 10 litres/min

 

[Scott_D]

Have you got an outside tap. Internal taps may have flow restrictors

 

[seb963]

Yes - I have just measured at the garden tap. Flow is much higher indeed, about 20L per min. The question is, would the flow have been even better with a 32mm ?
I am not too bothered by the downstairs taps because flow is ok, but I do worry about the flow I would get in the loft on hot and cold water, hence the question to know if a 32mm MDPE would habe maximised the chances of getting a better flow, or not.
Regards

 

[Ch4 plumbing]

If the builder has just run a new main in I would take a guess that you will need to have any and all filters and aerator's on the system cleaned of muck, grit and sand from the installation.

Also if you have paid SW to put a 32mm stopcock in then I would have expected the builder to run a 32mm Cold water main into the house!!

Has the builder had the new main inspected??

 

[joni os]

25mm is size recommended by most water companies for domestic properties when length of run less than 40 metres. If not getting 24 litres/min, at 40 metres, restriction is other than MDPE pipe.
Unless length exceeds 40 metres or you specifically asked for 32mm, Builder cannot be blamed on pipe size.
Flow at meter can easily be checked by standpipe. This would confirm there is not a problem with residual tag at tapping.

 

[seb963]

Thanks. Run of th 25mm MDPE is less than 40m. Thames Water stopcock is about 5 meters in front of the house. Flow at garden tap is about 20L/min.

 

[Ch4 plumbing]

25mm is size recommended by most water companies for domestic properties when length of run less than 40 metres. If not getting 24 litres/min, at 40 metres, restriction is other than MDPE pipe.
Unless length exceeds 40 metres or you specifically asked for 32mm, Builder cannot be blamed on pipe size.
Flow at meter can easily be checked by standpipe. This would confirm there is not a problem with residual tag at tapping.

For the cost involved of upgrading from 25mm to 32mm in materials why would the builder NOT just use 32mm MDPE if that is what the meter out let pipe size is?

Why pay for a meter upgrade and then not take advantage of it??

 

[joni os]

For the cost involved of upgrading from 25mm to 32mm in materials why would the builder NOT just use 32mm MDPE if that is what the meter out let pipe size is?

Why pay for a meter upgrade and then not take advantage of it??

Think we are reading OP differently. Supply pipe in road is 32mm but 32 mm stopcock most unlikely. Meter outlet pipe size usually 25mm for domestic, and water companies will resist installing larger size.

 

[ShaunCorbs]

Think we are reading OP differently. Supply pipe in road is 32mm but 32 mm stopcock most unlikely. Meter outlet pipe size usually 25mm for domestic, and water companies will resist installing larger size.

"Thames Water upgrade my mains connection to a 32mm MDPE," so i read that as 32mm to a meter or the stop tap?

 

[joni os]

"Thames Water upgrade my mains connection to a 32mm MDPE," so i read that as 32mm to a meter or the stop tap?

Perhaps OP will confirm if 25mm went straight into push fit connection at meter or if TW left 1 metre of 32 mm for external connection.
In my area the water company would be screaming, "Infrastructure Charge", for a straight 32mm run through.

 

[Ch4 plumbing]

Think we are reading OP differently. Supply pipe in road is 32mm but 32 mm stopcock most unlikely. Meter outlet pipe size usually 25mm for domestic, and water companies will resist installing larger size.

Yep I agree with you that a standard metre installation is 25mm MDPE but you can have 32mm MDPE if your property design requires a larger flow rate, it might not be easy but it is achievable.

Maybe the OP can clarify for us?

 

[Dotty]

"Thames Water upgrade my mains connection to a 32mm MDPE," so i read that as 32mm to a meter or the stop tap?

Perhaps OP will confirm if 25mm went straight into push fit connection at meter or if TW left 1 metre of 32 mm for external connection.
In my area the water company would be screaming, "Infrastructure Charge", for a straight 32mm run through.

Yep I agree with you that a standard metre installation is 25mm MDPE but you can have 32mm MDPE if your property design requires a larger flow rate, it might not be easy but it is achievable.

Maybe the OP can clarify for us?

I have just had Thames Water upgrade my mains connection to a 32mm MDPE, however my builder has run a 25mm MDPE after TW stopcock from the property boundary into the house,

Says it all, boys

 

[seb963]

I have attached a picture of the connection just after Thames Water stopcock. At the top is the MDPE pipe coming from the TW stopcock, at the bottom is the 25mm running into the house that the plumber fitted.
Looks like the pipe coming out from the stopcock is a 32mm?

 

[Dotty]

Is he really planning to bury that demountable fitting?

 

[joni os]

I stand corrected that is 32mm stepped down to 25mm and the builder must have realised when he purchased the fitting. Your £1100 cost misled me. Last time I wanted larger connection for nursing home, supplier wanted £5500 infrastructure charge and we ended up increasing cold water storage.

 

[seb963]

So does this mean the builder was correct to downsize to 25mm, or could he have carried on with 32mm inside the house to the internal stopcock?