HOW TO INCREASE FLOWRATE/PRESSURE TO NEW EN-SUITE

[AnthonyRad]

Hi all,

Bought a 3 bed semi and gutted it out completely. It's fed off of a 15mm incoming water mains pipe which then branches off in 15mm pipe to feed the bathrooms, boiler, kitchen etc.
It already has a relatively new Worcester Combi Boiler which I want to keep, a small downstairs loo (basin&toilet) and 1st floor bathroom with a thermostatic mixer. I’m planning to convert the loft and install an en-suite….

What do I need to do to increase the water pressure/flowrate to the loft en-suite so that the 2 showers can be on at the same time WITHOUT fitting an unvented cylinder??

• Can I keep the 15mm incoming mains as is and replace the 15 to 22mm pipe running to all the bathrooms?
• Do I ask the water company to upgrade the 15mm to a larger incoming supply pipe then branch off in 22mm or would 15 suffice?
• OR…(my preferred option) Can I just install an electric shower in the loft with a pump to give it the extra flowrate?

Thanks in advance. Anthony

 

[steadyon]

1. Nothing you do will increase the rate at which the boiler will produce hot water. Find the model number and look up its quoted hot water flow rate. This will be the maximum number of litres per minute of water heated from its incoming temperature by 35 degrees.
2. If you want two simultaneous showers from a boiler you will need either a large combi boiler, a storage combi boiler or stored hot water.
3. An electric shower (i.e. one which heats the water by electricity) must generally be run off the mains. You can't pump the mains by more than 12 litres per minute, and you would need to:
3a. Ensure your mains supply could cope.
3b. Make sure you aren't starving the boiler of water by pumping to another outlet.
4. I'd suggest you start by measuring the static and dynamic pressures, and the "open pipe" flow rate, of your cold mains at various times of various days. Armed with that data you will be in a better position to look at the options.

 

[Gasmk1]

depends on combi's size (output) as most combis will not cope with flow rate required for 2 shower simultaneously running

 

[AnthonyRad]

1. Nothing you do will increase the rate at which the boiler will produce hot water. Find the model number and look up its quoted hot water flow rate. This will be the maximum number of litres per minute of water heated from its incoming temperature by 35 degrees.
2. If you want two simultaneous showers from a boiler you will need either a large combi boiler, a storage combi boiler or stored hot water.
3. An electric shower (i.e. one which heats the water by electricity) must generally be run off the mains. You can't pump the mains by more than 12 litres per minute, and you would need to:
3a. Ensure your mains supply could cope.
3b. Make sure you aren't starving the boiler of water by pumping to another outlet.
4. I'd suggest you start by measuring the static and dynamic pressures, and the "open pipe" flow rate, of your cold mains at various times of various days. Armed with that data you will be in a better position to look at the options.

Thanks for your reply. Can you please tell me what the dynamic and static pressures are? I measured the flow rate:
12 litre bucket took 46 seconds to fill from the only current working tap in the house.
12/0.77 = 15.58 litres per minute

 

[steadyon]

1. Static pressure is the pressure measured at a point in the system, with no taps running. It's the "theoretical maximum" pressure you can get.
2. Dynamic pressure is the pressure measured at a point in the system, with at least one other tap running full bore.
3. The classic way of measuring is to attach a pressure gauge to an outside tap, then:
3a. Open the outside tap to measure the static pressure.
3b. Open the kitchen tap at the same time, and note the reading on the pressure gauge attached to the outside tap. This gives you the dynamic pressure.
3c. The readings above depend on there being no significant pressure reducing restrictions (long pipe runs, multiple elbows etc.) from the incoming main to either of the outside and kitchen taps.
4. To measure pressure you need a pressure gauge, such as Screwfix 82412.
5. The measurement of flow rate is highly influenced by restrictions. It is best measured at the kitchen tap, or an outside tap, again provided there a few restrictions, such as restricted bore isolation valves etc.
6. If you have the pressure (2.0 + bar dynamic and 20 litres / minute) you might consider an unvented hot water cylinder. This could be run off the central heating side of your existing combi boiler. Then you'd have 1 shower of the combi, in the normal way, and the other off the unvented cylinder, bot at mains pressure.

 

[king of pipes]

This has been discussed so many times on the forum there are ways to improve flow and pressure , wether it will get you vast improvement in a loft space bathroom is not guaranteed , firstly your incoming supply is only 15mm and by the information you have supplied it's within the water companies legal required supply to your property, if you had a lead supply coming in ? they may be willing to help you improve the supply, in the past I have installed a new 25mm mdpe into properties taking it to the old stopcock position the water company will then connect it free of charge? , minimum pipework size needs to be 22mm taken all the way to the combi and the loft ? the higher you go with a water supply there will be a drop off in pressure and flow and if someone uses water elsewhere in the property then this will also effect it there are various ways to go but improving the incoming supply is essential for a good result . Kop

 

[AnthonyRad]

1. Static pressure is the pressure measured at a point in the system, with no taps running. It's the "theoretical maximum" pressure you can get.
2. Dynamic pressure is the pressure measured at a point in the system, with at least one other tap running full bore.
3. The classic way of measuring is to attach a pressure gauge to an outside tap, then:
3a. Open the outside tap to measure the static pressure.
3b. Open the kitchen tap at the same time, and note the reading on the pressure gauge attached to the outside tap. This gives you the dynamic pressure.
3c. The readings above depend on there being no significant pressure reducing restrictions (long pipe runs, multiple elbows etc.) from the incoming main to either of the outside and kitchen taps.
4. To measure pressure you need a pressure gauge, such as Screwfix 82412.
5. The measurement of flow rate is highly influenced by restrictions. It is best measured at the kitchen tap, or an outside tap, again provided there a few restrictions, such as restricted bore isolation valves etc.
6. If you have the pressure (2.0 + bar dynamic and 20 litres / minute) you might consider an unvented hot water cylinder. This could be run off the central heating side of your existing combi boiler. Then you'd have 1 shower of the combi, in the normal way, and the other off the unvented cylinder, bot at mains pressure.

Hi, think i've got all the information together:

*Static pressure - 2.7 bar
*Dynamic pressure - 1 bar
*Boiler itself is a worcester greenstar 28i junior.
*flow rate: 12 litre bucket took 46 seconds to fill from the kitchen tap right next to the incoming mains supply. 12/0.77 = 15.58 litres per minute.

Granted the boiler will only power the thermostatic shower, just wondering with the above variables will I be able to run an electric shower in the loft off of 15mm pipe and then that and the thermostatic mixer both have enough pressure/flow rate work at the same time?

Cheers fellas

 

[king of pipes]

I very much doubt it as said before upgrade the incoming supply. Kop