Hot water pressure

[b3ak3r]

Hi, hoping someone might be able to offer some advice.

We've just replaced out bathroom and have gone from 2 separate taps on the sink and 1 dual flow tap on the bath to a single flow mixer tap on both.

The plumber has fitted a non-return valve on both the hot water supply to the sink and bath but now we get very little flow from the hot water. For example it now takes 80 seconds to pull any hot water through and a further 90 seconds to fill the sink.

The flow was never excellent but now is unworkable. The plumber has said this is due to the non-return valve. Would anyone know if it's possible to remove the non-return valve and fit a reduction valve to the cold water supply. Second question, if this is possible can anyone suggest a valve that can reduce the output down to .2 bar?

Many thanks.....

 

[Madrab]

True adding a check valve will stop the high pressure cold (mains I take it?) from pushing back on the hot water but If flow was already an issue then restricting the cold water would be the way to go. IMO he shouldn't have left you with an unreasonable hot water flow as that just isn't good practice and discussed other options with you. Given it's Cat2 water then a single check valve could be used but I don't believe he has installed them for back pressure protection or they'd be on the cold side too, rather than just to allow the hot to flow cause the cold pressure's too high. If the cold feeds have isolation valves on them then closing them partially may help but the check valves would need to be removed.
Most valve's operate between .5/1 and 6 bar and only seen one that goes down to .2 bar. http://www.dereve.co.uk/Dereve-Pressure-Regulators.htm

Is you hot water a gravity hot water cylinder?

 

[b3ak3r]

Thanks for your reply,

It is gravity fed and only about 1.8 meters below the bottom of the header tank. TBH i was a little disappointed that no other options were given when I asked about the flow and time for the water to heat up especially as looking online I found 3 other solutions.

I've just spoken to the tap manufacture and they said the taps should have a tolerance of about .5 so should be able to uses a prv that goes to 0.5 on the cold and get rid of the check valve on the hot. The other option i've seen is a pressure equalisation valve on hot and cold but not sure if this would also put some restriction on the hot similar to the check valve.

 

[Madrab]

TBH, I would have a chat to the plumber and discuss that the job isn't correct and can anything be done about it. There are other options as you suggest. A pressure equalising valve will lower the highest pressure to the same as the lowest pressure feed though it should not impeded the lower pressure's flow, but they aren't cheap.

 

[mfarrow]

The contamination risk is hot water getting into the cold mains. So just move the check valve from hot pipe to cold pipe. You can easily live with the pressure difference, and unless you're planning something stupid like blocking up the spout then I doubt cold backflow up the hot will be a problem, and anyway that's not a contamination risk, which is what check valves are for.

Likewise if both hot and cold are from your stored tank water then you shouldn't need any check valves.

 

[b3ak3r]

Thanks mfarrow

The cold is mains pressure and the hot is gravity fed. TBH i was thinking why i need the check valves because the bath taps which came out was a mixer tap which I believe was single flow and didn't have a valves fitted and we've had no issues with that for the past 4 years.

 

[b3ak3r]

I'm after a Pressure Reducing Valve 15mm compression with Gauge made by Intatec but can't find anywhere that stock it. Does anyone have any suggestions?

PRV22331510
SPECIFICATION

Adjustable pressure range: 0.5 - 6 bar
Factory set pressure: 3 bar
Max inlet pressure static: 16 bar
Maximum inlet temperature: 80°C

 

[Agile]

The problem you seem to have described is low flow rate on the HOT tap.

That is because you only have a 1.8m head to create the flow.

The check valve will not be helping but it is in my view essential.

The major restriction is likely to be the new tap because they are designed for high pressure supplies.

The best solution is a shower pump to boost the pressure!

The reason for the check valve is to prevent high pressure cold forcing water back up the hot pipe into the loft tank!

The simple situation is that you have inadequate hot pressure!

Tony

 

[b3ak3r]

Thanks Tony, the new taps are all low pressure ones.

 

[Agile]

Even low pressure taps are expected to still have a supply of about 0.5 bar for good flow rates. They usually suggest a minimum of 0.2 bar.

BUT their pressure is measured dynamically at the tap INLET and not just the static head with no flow!

You only have 0.18 bar before the pipe and non return valve resistances have been taken into account.

Its never sensible to fit mixer taps on unbalanced supplies! Customers usually specify these and the short of work plumbers still fit them even if they know they will not work well.

Many plumbers left school at 15 and don't really understand these things properly!

Tony