Low hot water pressure - cold is fine

[profet]

Quick question (hopefully)

I had my house fully re-plumbed a few years ago when we moved in with Worcester Green Star 42CDi combi boiler.

The cold water pressure is pretty good, but the hot water is poor - especially upstairs. We are getting a second bathroom fitted soon, so it's going to become a bigger problem.

Would the hot water normally drop just because it's being heated, or is something not set up right with the boiler.

What are my options?

Thanks for any help!

 

[Newboy]

Pressure or flowrate?

 

[profet]

Pressure or flowrate?

Definitely flow rate - 20 minutes plus to fill a bath. I assumed that was because of low pressure - how would I check?

 

[Newboy]

Ideally check the flow rate (how long to fill a known volume - a suitable container and a stopwatch) at the kitchen cold tap, kitchen hot, bathroom basin hot & bathroom basin cold.

If you can check the pressure with a suitable gauge - usually an outside stopcock/bibtap is the easiest.

The flow rate through the boiler will be lower than the flowrate for the incoming cold supply as the rise in temperature of the heated water is related to the flowrate through the boiler.

Running two bathrooms (and other demands for hot water) from a combi is usually not that practicable

 

[gasbanni]

Fitted a 40kw intergas on 25mm incoming mdpe hot water performance is fantastic according to the householder ! And she's got two bathrooms and a shower room.

Regarding the original question measure cold water temp, measure hot water temp, time how long to fill a large measurable container and check with the boiler spec.

Then you'll know if it's performing correctly or not.

 

[oldbutnotdead]

Plastic pipe or copper? What the others said about flow rate at various points (cold and hot)- a 5 litre tub and a stopwatch is a good starting point. Also if you have any documentation on the taps see if any are fitted with flow restrictors..... (got caught out with them once before).
Final one- was the place completely replumbed or just converted from open vent to combi? Reason I ask- you might have an airlock at the original high point on the pipework (where the cylinder used to be) which would reduce your flow rate especially upstairs. If there's a massive differential between cold flow/hot flow downstairs and upstairs then that is a possible (eg if downstairs you get 20l/min cold and 10l/min hot you could expect upstairs 18l/min cold and 9 l/min hot- same relative performance. If upstairs you're getting 18l/min cold and 5 l/min hot then something is wrong- see above)

Also, if the place was completely replumbed do you have automatic mixer valves anywhere?